Institute for Quantum Computing
Institute for Quantum Computing
News Article | April 17, 2017
Novel fabrication of diamond nanophotonics coupled to single-photon detectors Diamond nanophotonics is a rapidly evolving platform in which non-classical light—emitted by defect centers in diamond—can be generated, manipulated, and detected in a single monolithic device (e.g., for quantum information processing applications).1–3 Indeed, novel diamond fabrication techniques make it possible to engineer unique nanostructures in which diamond's extraordinary material properties (e.g., high refractive index, wide band gap, and large optical transmission window) can be exploited.4, 5 The relatively large Kerr non-linearity6 of diamond also makes it an attractive platform for on-chip nonlinear optics at visible and IR wavelengths.7 This nonlinearity could be used for frequency conversion of photons generated by color centers in diamond (i.e., from their typical visible wavelengths to telecom wavelengths).8 In turn, this would enable transmission of quantum information and distribution of quantum entanglement9, 10 over long distances. Such integrated diamond–quantum photonics platforms would benefit from the use (and realization) of high-performance single-photon detectors that have broadband photon sensitivity and are integrated on the same diamond chip. Superconducting nanowire single-photon detectors (SNSPDs) are a class of cutting-edge photon detectors that outperform other technologies in terms of detection efficiency, dark counts, timing jitter, and maximum count rates.11–13 SNSPDs typically consist of narrow nanowires that are patterned into an ultrathin (4–8nm) superconducting film.14 The nanowires are biased close to the critical current of the superconductor material so that when an incident photon is absorbed by the wire, a small resistive hotspot forms and generates a voltage pulse, which is amplified and measured.15 In our work,16,17 we have developed a novel fabrication procedure with which we can etch freestanding diamond nanostructures directly from a bulk substrate. We use these freestanding diamond waveguides to guide the emission from diamond color centers—nitrogen18 or silicon vacancies (NVs or SiVs), see Figure 1, that we implant within the waveguides—to evanescently coupled niobium titanium nitride SNSPDs. The evanescently coupled SNSPDs can thus be used to detect the color center fluorescence, while filtering out the pump laser that scatters into the waveguide. A scanning electron microscope image of several freestanding diamond waveguides (with triangular cross sections) is shown in Figure 2(a). We etched these waveguides from single-crystal diamond with the use of our angled-etching fabrication method.4 The waveguides are supported periodically by thin support structures underneath the waveguide that are created by slightly increasing the width of the waveguide at the support locations. This allows long segments of the waveguide to remain freestanding (while not perturbing the waveguide mode).19 In addition, single meander SNSPDs—see Figure 2(b)—are located on both ends of the waveguide. The SNSPDs are then connected to titanium/gold contact pads for electrical readout. Finite-difference time-domain simulations of the diamond waveguide SNSPD device are shown in Figure 3. The normalized field distribution of the optical mode in the diamond waveguide is shown in Figure 3(a), which illustrates the capacity for single-mode waveguide operation in the triangular cross section diamond waveguide. In addition, the absorption characteristics of the device—Figure 3(b)—indicate that more than 99% of the optical power has been absorbed by the SNSPD after a propagation distance of 15μm. The photon-counting performance of an SNSPD on one of the freestanding diamond waveguides (at 4.2K)—when illuminated with vertically incident 705nm photons—is depicted by the blue curve in Figure 4, and the red curve indicates the dark count response of the detector. The temperature (4.2K) and superconductor thickness (10.5nm) of the device limit the SNSPD from reaching a fully saturated photon count rate. However, we do observe a wide photon-counting operational range (i.e., the region where the device count rate begins to level off and approach an ideal saturated regime) that is still far from the detector's intrinsic dark counts. In summary, we have developed a platform with which SNSPDs can be fabricated on freestanding waveguides that are etched from single-crystal diamond (which can host quantum emitters with good spectral properties).20 We have also characterized the photon-counting performance of our fabricated detectors. With our approach it is possible to achieve monolithic and scalable integration of diamond quantum optical circuits that are based on defect color centers. In the next stages of our work, we plan to improve the filtering of the pump beam (i.e., that is used to excite the color centers) so that the SNSPDs are no longer saturated by pump photons. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (NSF) award ECS-0335765. CNS is part of Harvard University. We also acknowledge the financial support of the Ontario Centres of Excellence, the Natural Sciences and Engineering Research Council of Canada, and the Institute for Quantum Computing. This work was also partly supported by the Science and Technology Center (STC) for Integrated Quantum Materials (by NSF grant DMR-1231319) and the Harvard Quantum Optics Center. Robert Westervelt was supported by the STC for Integrated Quantum Materials by NSF grant DMR-1231319.
News Article | August 22, 2016
MIT Physics Department Senior Research Scientist Jagadeesh S. Moodera was one of the pioneers in the field of spin-polarized magnetic tunnel junctions, which led to a thousand-fold increase in hard disk storage capacity. Using his group’s expertise working with atomically thin materials that exhibit exotic features, Moodera is laying a step-by-step foundation toward a new generation of quantum computers. Moodera’s group is making progress toward devices that display resistance-free, spin-polarized electrical current; memory storage at the level of single molecules; and capture the elusive paired electron “halves” known as Majorana fermions, which are sought after as qubits for quantum computing. This work combines materials that allow the free flow of electrons only on their surface (topological insulators) with other materials that lose their resistance to electricity (superconductors). Researchers call mixed layers of these materials heterostructures. A key goal is to push these effects up from ultracold temperatures to ordinary temperatures for everyday use. “Our group specializes in the growth and understanding the physical phenomena at the atomic level of any number of exotic combinations of these materials plus heterostructures with different other materials such as ferromagnetic layers or superconductors and so on,” Moodera says. Majorana fermions, which can be thought of as a paired “electron halves,” may lead to creating quantum entanglement believed necessary for quantum computers. “Our first goal is to look for the Majorana fermions, unambiguously detect them, and show this is it. It’s been the goal for many people for a long time. It’s one of those things predicted 80 years ago, and yet to be shown in a conclusive manner,” Moodera says. Moodera’s group is searching for these Majorana fermions on the surface of gold, a phenomenon predicted in 2012 by William and Emma Rogers Professor of Physics Patrick Lee and Andrew C. Potter PhD ’13. “I have a lot of hope that it’s going to come up with something very interesting, this particular area is exotically rich,” Moodera says. His team reported progress toward this goal in a Nano Letters paper published on March 4. Postdoc Peng Wei, with fellow Moodera group postdocs Ferhat Katmis and Cui-Zu Chang, demonstrate that epitaxial (111)-oriented gold thin films become superconducting when grown on top of superconducting vanadium film. The vanadium becomes a superconductor below 4 kelvins, which is hundreds of degrees below room temperature. Tests show that the surface state of (111)-oriented gold also becomes superconducting, which holds out potential for this system in the search for Majorana fermions. Future work will seek to detect Majorana fermions on the ends of (111)-oriented gold nanowires. “In this kind of nanowire, in principle, we would expect Majorana fermion states to exist at the end of the nanowire instead of in the middle,” Wei explains. Moodera says, “We have not discovered Majorana fermions yet, however, we have made a very nice foundation for that.” Further results will be published soon. In a series of 2015 papers, Moodera’s group demonstrated the first reported truly zero-resistance edge current in the quantum anomalous Hall state of a topological insulator system, realizing a 1988 prediction by F. Duncan M. Haldane at Princeton University. The importance of comprehensive achievements of perfect quantum anomalous Hall state at zero magnetic field as well as the demonstration of dissipationless chiral edge current in a topological insulator is well brought out in a Journal Club for Condensed Matter Physics commentary by Harvard University Professor Bertrand I. Halperin, a pioneer in the field. “In this system, there is a very special edge state. The bulk is insulating, but the edge is metallic,” says Cui-Zu Chang, lead author of the Nature Materials paper and Physical Review Letters paper published in April and July 2015. “Our group is the first to show a completely dissipationless edge state, meaning that the resistance for current flow exactly becomes zero when the quantum state is reached at low temperatures,” Chang says. “If one can realize this effect, for example, at room temperature, it will be remarkably valuable. You can use this kind of effect to develop quantum electronics including the quantum computer,” Chang says. “In this kind of computer, there is minimal heating effect; the current flow is completely dissipationless; and you can also communicate over very long distance.” In a 2013 paper with collaborators from Northeastern University, Göttingen University in Germany and Spence High School in New York, Moodera and MIT postdoc Bin Li demonstrated a superconducting spin switch in a structure sandwiching an aluminum layer between europium sulfide layers. In this work, the intrinsic magnetization of europium sulfide controls superconductivity in the aluminum layer. The direction of magnetization in europium sulfide can be reversed, which can thereby switch the aluminum between superconducting and normal states, making it potentially useful for logic circuits and nonvolatile memory applications a step in the direction of superconducting spintronics. These experiments validated a theoretical prediction 50 years ago by French Nobel Laureate Pierre-Gilles deGennes. Several years ago Guoxing Miao, then a junior researcher with Moodera, observed a unique energy profile across a sandwich structure made with metallic islands confined within two europium sulfide magnetic insulator barriers. This arrangement of the inherent large energy separation in the nano islands combined with the large interfacial magnetic field confined at the interface and the spin selective transmission property of the adjacent europium sulfide powerfully modifies the two-dimensional electronic structures. They observed spin-assisted charge transfer across such a device, generating a spontaneous spin current and voltage. These unique properties can be practical for controlling spin flows in electronic devices and for energy harvesting. Published in Nature Communications in April 2014, these were unexpected fundamental results, Moodera says. Guoxing Miao is an assistant professor at University of Waterloo and Institute for Quantum Computing in Canada. More recently, the researchers paired europium sulfide with graphene, creating a strong edge current, which they reported March 28 in Nature Materials. “What we find is very exciting,” postdoc Peng Wei, lead author of the paper, says: “Experiments show a strong magnetic field (more than 14 Tesla) experienced by graphene originating in the europium sulfide that polarizes the spins of electrons in the graphene layer without affecting the orbital motion of the electrons.” In the device, europium sulfide produces a large field, called a magnetic exchange field, which raises the energy of spin-up electrons and lowers the energy of spin-down electrons in graphene and creates an edge current with spin-up electrons streaming in one direction and spin-down electrons streaming in the opposite direction. These effects are brought about by the confinement of electrons in these atomically thin devices, fellow postdoc Ferhat Katmis explains. At the interface between europium sulfide, which is a magnetic insulator, and graphene, Peng Wei explains, the graphene can “feel” the huge exchange field, or internal magnetism, which can reach millions times bigger than the Earth’s magnetic field, from the europium sulfide. This effect is potentially useful for spin-based memory and logic devices and possibly quantum computing. Moodera was a guest editor of the July 2014 MRS Bulletin, which highlighted progress in organic spintronics. Controlling magnetic behavior at the interface of the materials is again the key element in this approach. By adding magnetic sensing capability to these large organic molecules (up to hundreds of atoms per molecule), their magnetic orientation can be switched back and forth. This work holds promise to serve as photo-switches, color displays, and information storage units at the molecular level. These molecules can start out completely non-magnetic, but when they are placed on the surface of a magnetic material, their behavior changes. “They share electrons at the interface. These molecules share some of their electrons into the ferromagnetic layer or the ferromagnetic layer actually gives out some of its electrons carrying with it the magnetic behavior,” Moodera explains. Electrons from the magnetic material carry a magnetic signature, which influences the organic molecule to switch between resistive and conductive states. This collaborative work between researchers in the U.S., Germany, and India was published as a Nature Letter paper in 2013. Moodera and co-inventor Karthik V. Raman PhD ’11 were issued a patent in May 2014 for high-density molecular memory storage. It is one of four patents issued to Moodera and colleagues. “We have shown early stages of such a possibility of these molecules being used for storing information,” Moodera says. “This is what we want to explore. This will allow us to store information in molecules in the future.” He projects that molecular storage can increase storage density by 1,000 to 10,000 times compared to current technology. “That gives you an idea of how powerful it can become,” he says. Organic molecules have other advantages as well, he says, including lower cost, less energy consumption, flexibility and more environmentally friendly materials. “But it’s a very, very huge area, almost untapped direction where many unprecedented new phenomena might emerge if it can be patiently investigated fundamentally,” he cautions. Moodera is currently seeking long-term funding for this research into permanent memory devices using magnetic single molecules. “It’s a visionary program which means somebody has to be patient,” Moodera explains. “We are quite capable of doing this here if we get good support. ... Everything has to be looked at and understood, and then go further, so there is no set a priori recipe for this!” In 2009, Moodera and two MIT colleagues (the late Robert Meservey and Paul Tedrow, then group leader) shared the Oliver E. Buckley Condensed Matter Prize from the American Physical Society with Terunobu Miyazaki from Tohuku University in Japan for "pioneering work in the field of spin-dependent tunneling and for the application of these phenomena to the field of magnetoelectronics (also called spintronics)." “Jagadeesh Moodera and team were the first to show magnetoresistance from a magnetic tunnel junction at room temperature — a fundamental discovery that has enabled rapid growth of data storage capacity. All hard disk drives made since 2005 have a MTJ as the read sensor,” says Tiffany Santos ’02, PhD ’07, a former Moodera lab member who now works as a principal research engineer at HGST in San Francisco. As a materials science undergraduate and then doctoral student in Moodera's group, Santos explored spin-polarized tunneling in MTJs made of novel materials such as magnetic semiconductors and organic molecules. Santos was awarded best thesis prize from the Department of Materials Science and Engineering both for her BS and PhD theses. In common bar magnets, which have north and south poles, two magnets are attracted if opposite poles face, but will repel if the same poles face each other. Similarly, in a magnetic tunnel junction, the current flow across the layered materials will behave differently depending on whether the magnetism of the layers points in the same, or in the opposite, direction — either resisting the flow of current or enhancing it. This spin tunneling work, which dates to the 1990s, revealed that pairing two thin magnetic materials separated by a thin insulator causes electrons to move, or “quantum tunnel,” through the insulator from one magnet to the other, which is why it is called a magnetic tunnel junction. “This change in the current flow, very significant, can be detected very easily,” Moodera says. Since these magnetic materials are atomically thin, rather than north and south poles, their magnetism is associated with the up or down spin of electrons, which is a quantum property, and they are characterized as parallel when their spins are in alignment, or antiparallel when their spins point in the opposite directions. “So all you have to do is change from parallel to anti-parallel orientation, and there you have this beautiful spin sensor, or spin memory,” Moodera says. “This spin memory is non-volatile; that’s the most striking thing about it. You can set this particular device in a particular orientation, leave it alone, after a million years it’ll be still like that; meaning that the information which is stored here will be permanent.” Institute Professor Mildred S. Dresselhaus has known Moodera for many years, initially through his work using magnetic fields for materials research. Moodera, she says, developed expertise in spin phenomena long before they became popular topics in science and he has attained similar status in topological insulators. “His career has been all like that. He works for the love of science, and he’s not particularly interested in recognition,” Dresselhaus adds. Although Moodera has never been a faculty member, he works effectively with students and he finds his own support, she notes. “MIT is a place that can accommodate people like him,” Dresselhaus says. Limited funding means the U.S. is in danger of losing its leadership role in research, Moodera fears. He involves high school students and undergraduates (nearly 150 so far) in his research, many becoming coauthors in the publications and patents. “When we tell the young students and postdocs, ‘Oh, physics is wonderful, you should get into research, you really can discover many things that are exciting and valuable’, we are not actually telling the whole story. Despite funding support from National Science Foundation and Office of Naval Research for our program, there is increasing uncertainty and pressure to raise research funds. ... With constant struggle for funds, one spends much time in dealing with these issues. ... We wish there is reliable and continuous support when the track record is good. Science is like art — if creative breakthroughs are needed, then the proper support should be there with long-term vision, with freedom to explore, and without breaks and uncertainties. When one looks at some of the breakthroughs we have achieved so far — magnetic tunnel junctions that drives all hard drives in computers, prototype molecular spin memory, nonvolatile perfect superconducting spin memory/switch or even the latest totally spin-polarized edge current which is perfectly dissipationless, evidently the foundations for tomorrow’s cutting edge technology, isn’t it crystal clear that such a research program be unequivocally supported to benefit our society?” he asks. Despite his lab’s prominence in spintronics and topological insulators, making further progress in the current research environment means he depends on federal and other outside grants. “If I don’t have funding, I close the shop,” he says. “Everything moves so fast, you cannot wait for tomorrow. Everything has to happen today, that’s the unfortunate thing dealing with uncertainty. It’s a lot of pressure and stress on us, particularly in the last 10 years. The funding situation has become so volatile that we are kept under the dark cloud, constantly concerned about what is coming next.” Yet the situation has not always been so. During a tour of his lab facilities, Moodera recalls a phone call (over 20 years ago) from an Office of Naval Research (ONR) program director, Krystl Hathaway, who suggested there was money available, his work was high-quality, and that he should apply. “That was when I had only a month or two of funds left to sustain a research program! So, I said yes! I couldn’t believe it in the beginning,” he recalls. “I put in a one-page application. In a week’s time she sent me the money to tidy me out for four months. After that, I put in a real, several-page proposal for a full grant, and she supported my research program for over 10 years. Two years after this support started, research led to the discovery of the phenomenon called the tunnel magnetoresistance in 1994-95, which besides creating a vast new area of research, is also instrumental in the explosion of unbelievable storage capacity and speed in computer hard drives as we enjoy today at rock bottom cost. Most notable is that this work was mainly done with a summer high school intern who later joined MIT [Lisa Kinder, '99] and an undergraduate [Terrilyn Wong '97].” Later, when the same program officer was at a Materials Research Society (MRS) meeting in Boston, she visited Moodera’s lab and noticed the age of a key piece of thin film equipment used in creating the tunnel magnetoresistance breakthrough. It was then about 35 years old and had been cobbled together mostly from salvaged parts. Again she volunteered to provide substantial funding to build specialized equipment for a technique called molecular beam epitaxy (MBE), which is used to create ultra-clean thin films, atomic layer by atomic layer. On vacation in India, Moodera got a phone call from a physics administrator (the late Margaret O'Meara), telling him Hathaway from ONR was urgently looking for him. “I came back the next day, and then I spent four hours writing a proposal, which another two hours later was submitted from MIT. It all happened in one day essentially, and one week later I got $350,000, which built our first MBE system,” he says. “It’s a very versatile system that even after 20 years continues to deliver big results in the growth and investigation of the field of quantum coherent materials at present. By carefully planning and optimizing we even got some other critical parts that we needed for our other equipment in the lab.” “Dr. Hathaway, and then subsequently Dr. Chagaan Baatar, the new program director at ONR, were very happy that we produced a lot more things in the new system. It made a huge difference in our program. So that’s how sometimes it works out, and fundamental research should be supported if one looks for breakthroughs!” he says. “People come in and see, 'these people need support'. So that kind of thing should happen now, I think.” Funding for basic science has to increase by manyfold, Moodera suggests. “The future is actually created and defined now. Evidently it’s very important then. If you don’t invest now, there is no future development. A vision for fundamental knowledge buildup is strongly eroding in the country now, and thus needs to be corrected before it reaches the point of no return,” he says. Moodera has been at MIT for over three decades, where his group is part of the Francis Bitter Magnet Laboratory (which is now under Plasma Science and Fusion Center) and the Department of Physics. Moodera’s lab equipment ranges from the newest two-story scanning tunneling microscope that can examine atomic surfaces and molecules under extreme cold and high magnetic fields to a 1960s’ vintage glass liquid helium cryostat, which still sees frequent use. “It’s not the equipment. It’s how you think about a problem and solve it, that’s our way of looking at things. ... We train real scientists here; ones that can really think, come up with something out of essentially nothing. To start from basic atoms and molecules and actually build things, completely new and understand the emerging phenomena; unexpected science can come out of it,” Moodera says. “This group has solved important physics in ferromagnetism,” postdoc Peng Wei says. “We actually have very unique equipment that cannot be seen in other labs.” A native of Bangalore, India, Moodera plays badminton, ping-pong, and tennis, and he follows world tennis, soccer, and cricket. With his wife, MIT Department of Materials Science and Engineering senior lecturer Geetha Berera, Moodera likes to hike and enjoy nature. His hobbies include gardening and bird watching.
News Article | April 5, 2016
Shifting the colour of a photon, or changing its frequency, is necessary to optimally link components in a quantum network. For example, in optical quantum communication, the best transmission through an optical fibre is near infrared, but many of the sensors that measure them work much better for visible light, which is a higher frequency. Being able to shift the colour of the photon between the fibre and the sensor enables higher performance operation, including bigger data rates. The research, published in Nature Communications, demonstrated small frequency shifts that are useful for a communication protocol known as wavelength division multiplexing. This is used today when a sender needs to transmit large amounts of information through a transmission so the signal is broken into smaller packets of slightly different frequencies and sent through together. The information is then organized at the other end based on those frequencies. In the experiments conducted at NRC, the researchers demonstrated the conversion of both the frequency and bandwidth of single photons using a room-temperature diamond quantum memory. "Originally there was this thought that you just stop the photon, store it for a little while and get it back out. The fact that we can manipulate it at the same time is exciting," said Kent Fisher a PhD student at the Institute for Quantum Computing and with the Department of Physics and Astronomy at Waterloo. "These findings could open the door for other uses of quantum memory as well." The diamond quantum memory works by converting the photon into a particular vibration of the carbon atoms in the diamond, called a phonon. This conversion works for many different colours of light allowing for the manipulation of a broad spectrum of light. The energy structure of diamond allows for this to occur at room temperature with very low noise. Researchers used strong laser pulses to store and retrieve the photon. By controlling the colours of these laser pulses, researchers controlled the colour of the retrieved photon. "The fragility of quantum systems means that you are always working against the clock," remarked Duncan England, researcher at NRC. "The interesting step that we've shown here is that by using extremely short pulses of light, we are able to beat the clock and maintain quantum performance." The integrated platform for photon storage and spectral conversion could be used for frequency multiplexing in quantum communication, as well as build up a very large entangled state – something called a cluster state. Researchers are interested in exploiting cluster states as the resource for quantum computing driven entirely by measurements. "Canada is a powerhouse in quantum research and technology. This work is another example of what partners across the country can achieve when leveraging their joint expertise to build next-generation technologies," noted Ben Sussman, program leader for NRC's Quantum Photonics program. More information: Kent A. G. Fisher et al. Frequency and bandwidth conversion of single photons in a room-temperature diamond quantum memory, Nature Communications (2016). DOI: 10.1038/ncomms11200
News Article | April 7, 2016
Home > Press > Changing the color of single photons in a diamond quantum memory Abstract: Researchers from the Institute for Quantum Computing at the University of Waterloo and the National Research Council of Canada (NRC) have, for the first time, converted the colour and bandwidth of ultrafast single photons using a room-temperature quantum memory in diamond. Shifting the colour of a photon, or changing its frequency, is necessary to optimally link components in a quantum network. For example, in optical quantum communication, the best transmission through an optical fibre is near infrared, but many of the sensors that measure them work much better for visible light, which is a higher frequency. Being able to shift the colour of the photon between the fibre and the sensor enables higher performance operation, including bigger data rates. The research, published in Nature Communications, demonstrated small frequency shifts that are useful for a communication protocol known as wavelength division multiplexing. This is used today when a sender needs to transmit large amounts of information through a transmission so the signal is broken into smaller packets of slightly different frequencies and sent through together. The information is then organized at the other end based on those frequencies. In the experiments conducted at NRC, the researchers demonstrated the conversion of both the frequency and bandwidth of single photons using a room-temperature diamond quantum memory. "Originally there was this thought that you just stop the photon, store it for a little while and get it back out. The fact that we can manipulate it at the same time is exciting," said Kent Fisher a PhD student at the Institute for Quantum Computing and with the Department of Physics and Astronomy at Waterloo. "These findings could open the door for other uses of quantum memory as well." The diamond quantum memory works by converting the photon into a particular vibration of the carbon atoms in the diamond, called a phonon. This conversion works for many different colours of light allowing for the manipulation of a broad spectrum of light. The energy structure of diamond allows for this to occur at room temperature with very low noise. Researchers used strong laser pulses to store and retrieve the photon. By controlling the colours of these laser pulses, researchers controlled the colour of the retrieved photon. "The fragility of quantum systems means that you are always working against the clock," remarked Duncan England, researcher at NRC. "The interesting step that we've shown here is that by using extremely short pulses of light, we are able to beat the clock and maintain quantum performance." The integrated platform for photon storage and spectral conversion could be used for frequency multiplexing in quantum communication, as well as build up a very large entangled state - something called a cluster state. Researchers are interested in exploiting cluster states as the resource for quantum computing driven entirely by measurements. "Canada is a power-house in quantum research and technology. This work is another example of what partners across the country can achieve when leveraging their joint expertise to build next-generation technologies," noted Ben Sussman, program leader for NRC's Quantum Photonics program. About University of Waterloo University of Waterloo is Canada's top innovation university. With more than 36,000 students we are home to the world's largest co-operative education system of its kind. Our unmatched entrepreneurial culture, combined with an intensive focus on research, powers one of the top innovation hubs in the world. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
News Article | October 5, 2016
Quantum physics, with its descriptions of bizarre properties like entanglement and superposition, can sound like a science fiction fever dream. Yet this branch of physics, no matter how counterintuitive it seems sometimes, describes the universe all around us: As physicists have told often told me, we live in a quantum world. Soon, this will be better reflected in our technology, and everything it can do. "We're moving towards a new paradigm for computation," quantum information scientist Michele Mosca, who's based at the Institute for Quantum Computing at the University of Waterloo, recently told me. He compared this shift in thinking to when humanity abandoned the flat Earth hypothesis and accepted that our world is round. "We realized that [our pictures of the surface of the Earth] should embed on a sphere, not a flat surface," he said. "Now our maps make sense." Before, we were looking at them the wrong way, and the picture was distorted. Not anymore. Read More: Scientists Set a New Distance Record for Quantum Teleportation This new quantum paradigm "brings new possibilities," Mosca continued, "for computing, for communication, for sensing and measuring." In a public lecture delivered on Wednesday from the Perimeter Institute for Theoretical Physics, Mosca will describe the "new quantum era" and the promises and challenges it brings. Take, for example, public key cryptography that is used to protect secret communications around the world. When the first true quantum computer powers up, maybe a decade from now, it's predicted that it will be able to crack this type of encryption, no problem. Mosca has been urging governments and corporations to start planning for this. Mosca's talk, which begins at 7 pm E.S.T., will be livestreamed here on Motherboard. If you have questions about the future of quantum, scientists will be answering at Perimeter's Facebook page or on Twitter, using the hashtag #piLIVE. Get six of our favorite Motherboard stories every day by signing up for our newsletter.
News Article | September 20, 2016
Scientists have teleported the quantum state of a light particle over six kilometers (roughly 3.7 miles), setting a new distance record for quantum teleportation—and taking another step towards creating an internet that's secure from hacking threats, including those posed by future quantum computers. The challenge here is that so much of our communications—whether banking transactions, personal health information, or classified government files, to name a few examples—rely on cryptographic tools that quantum computers, once they become available, will be able to crack. Current cybersecurity attacks "exploit things like faulty implementation, or an insider threat," Michele Mosca, co-founder of the Institute for Quantum Computing at the University of Waterloo, told me. "They can be very costly, but when they're detected, you can fix it." Cryptographic tools "generally rely on some math problem being hard," Mosca continued. What might be difficult or impossible for a classical computer to solve—for example, factoring a very large number into primes—will not necessarily challenge a quantum machine. Of course, nobody knows for sure when the first true quantum computer will be available, although it's getting closer. Mosca authored a recent report estimating a one-in-seven risk that, within a decade, emerging quantum technologies will undermine some of the most important public key cryptography systems, which are widely used today to protect data online—and a 50 percent chance that many of them will be obsolete by 2031. Once a nation-state (or eventually a well-funded criminal group) gets its hands on a quantum computer, "we're not talking about a patch-up job," said Mosca, who is presenting at a conference this week in Toronto that addresses the future quantum threat to businesses and governments. "When your foundations are broken, there's no way to fix it." Read More: Government Must Prepare for When Quantum Computers Can Crack Its Encryption The US National Security Agency and others have announced their intention to switch over to "quantum-safe" systems, although scientists are still working out what exactly that means. Which brings us back to quantum teleportation. According to physicist Wolfgang Tittel of the University of Calgary, quantum cryptography could keep communications safe. Although the verdict is still out on many other systems, "we know for sure that quantum key distribution is not vulnerable to a quantum computer," Tittel told me. He is lead author of a new study, published alongside a similar demonstration from a Chinese team, in Nature Photonics. The teleportation experiment relied on what Einstein famously called "spooky action at a distance"—quantum entanglement, which means that two particles share certain properties even over large distances. Here, scientists temporarily took over part of the city of Calgary's fiber optic cable network to send the signal. It's not that an entire photon (or light particle) was sent via the cable, Tittel emphasized. "The transfer happens in a disembodied manner," he explained. "The state [of the particle] appears on the receiver side, without the particle travelling." Part of the magic of quantum mechanics is that, when a system is directly observed, it collapses. "There's no way to observe it without changing it," he said. "The receiver would see, and know it's been tampered with." That makes for a great guarantee that there are no eavesdroppers on the line, but it also presents a challenge for transmitting communications over distances greater than 200 kilometers, Tittel said. He and others are trying to get around it by designing quantum repeaters, which would be similar to those that are used in current communications to carry messages over long distances, but ones that are quantum-friendly. "A real quantum repeater will require teleportation and quantum memory," like a hard disk that stores information, Tittel said. "We did the teleportation part," and he hopes to make an advance on quantum memory soon. Tittel's goal is to "build a quantum network for quantum key distribution" across Calgary, then Alberta, then all of Canada, he told me, "and to [eventually] connect to quantum computers, which I believe will be available in ten-to-twenty years." Waterloo, where Mosca is based, has earned a reputation as Quantum Valley. When we spoke, Mosca emphasized that quantum technologies hold immense promise, but that we still need to prepare ourselves for their arrival—which means strengthening our cybersecurity systems now. "We have to make sure we can continue to communicate in secrecy," Tittel said. Get six of our favorite Motherboard stories every day by signing up for our newsletter.
News Article | April 17, 2016
Few things go together as poorly as science and politicians. Whether it’s Senator Ted Stevens describing the internet as a “series of tubes” during a net neutrality debate or Republican representatives reveling in their own ignorance about climate change, it’s clear that scientific illiteracy is a rampant problem in our nation’s hallowed halls of government. Yet this was precisely why it was so refreshing to see Canada’s recently elected Prime Minister Justin Trudeau explain the difference between a “normal” computer and a quantum computer completely off the cuff during a press briefing at the Perimeter Institute in Waterloo, Ontario, thereby proving that politics and science need not be mutually exclusive. Although Trudeau was at the Institute to announce $50 million in funding which will allow those working at Perimeter to continue their work on fundamental physics, he took the time to breakdown the essence of quantum computing for a clueless journalist: “Normal computers work either with power going through a wire or not, a one or a zero,” Trudeau said. “They’re binary systems. What quantum states allow for is much more complex information to be encoded into a single bit. A regular computer bit is either a one or a zero, on or off. A quantum state can be much more complex than that because as we know things can be both a particle and a wave at the same time, and the uncertainty around quantum states allows us to encode more information into a much smaller computer. That’s what’s exciting about quantum computing.” While most applauded Trudeau’s remarkably “clear and concise” explanation of quantum computing, others deemed his description as totally off the mark. I decided to ask some experts on quantum computing what they thought of the Prime Minister’s explanation to settle the debate once and for all: Romain Alléaume—Associate Professor at Telecom ParisTech and Paris Center for Quantum Computing “The beginning of Justin Trudeau’s explanation, about the difference between a classical bit and a quantum bit is absolutely correct. To be frank, the argumentation of Justin gets gradually more ‘uncertain’ when he says that the uncertainty principle implies that we can encode more information into ‘smaller computers’. Maybe he wanted to say that quantum computers can process information ‘in superposition,’ which allows to speed up some computations (i.e., solve some problems on smaller computers), but I am not certain about that. It is great to see a high level politician show enthusiasm for one of the biggest challenges in modern science.” Amr Helmy—Director, University of Toronto’s Center of Quantum Information and Quantum Control “His account of the distinction between a classical and quantum state is accurate. This is impressive that Canada’s PM has given this some thought. His comment on how superposition aides in storing information is an argument that can be equally made to explain the power which quantum computing possesses to process information in a fashion that is distinctly different from the classical paradigms. These are insights that are rarely considered by a Prime Minister. The rest of the world should be jealous!” SCORE: Too complex an issue to rank Michele Mosca—University Research Chair and Co-founder, Institute for Quantum Computing, University of Waterloo. Founding Member, Perimeter Institute for Theoretical Physics "The task is to explain quantum computing to a lay audience in a 100 words or so. It’s extremely hard, for even the best scientists and communicators, to get something like this both correct and interesting, especially in 100 words. He doesn’t say anything wrong. He conveys the essence of what quantum computing is, and why it might be more powerful. It’s understandable, and succinct. Also, keep in mind that this was something he said live, on the fly, in response to a joke from a reporter. Room for improvement? Hard to find. Can he next explain how encoding that more complex information in quantum bits leads to a more powerful computer? I’d love to hear his explanation." Aephraim Steinberg—Professor of Physics at the University of Toronto and member of Center of Quantum Information and Quantum Control “He zeroed in on the importance of how information is stored in a physical system, what a bit is, and the difference between classical bits and ‘quantum bits’ or ‘qubits’. This hinted he may have appreciated something very deep: the field of quantum computing is not just about trying to figure out how to speed up one task or another, but about understanding the fundamental role information has in the laws that govern the universe, how much information it takes to describe a physical system, and, on the flip side, what it means to store information in a physical system. “He faltered when trying to explain why a qubit is so much richer than a classical bit and threw in a few tangentially related buzzwords like ‘uncertainty’ and ‘particle and wave,’ in a way that made it clear that although he had the (accurate) sense that these concepts had something to do with quantum information he had to admit that he didn’t know what the connection was, but would throw caution to the wind and stir up some buzzword soup. “To put it bluntly, if you think about the level at which any scientist given a few minutes to try to explain quantum computing to him would have tried to pitch it, he probably got the gist and explained it back as well as you could imagine anyone doing. In any case, my joy is not because I believe our Prime Minister has become an expert at quantum physics. It is because he showed that he is ready to listen to scientists and try to understand what they are saying, what they believe is important, and why they demand support for basic research.”
News Article | October 28, 2016
Christie® projectors are bringing quantum science to life in a new exhibit at THEMUSEUM in downtown Kitchener, Ontario. QUANTUM: The Exhibition will run from October 14, 2016 – January 1, 2017, and then depart on a Canada-wide tour throughout 2017. QUANTUM shares the wonders of the quantum world and emerging quantum technologies with attendees. Part of the exhibition, the introductory experience, features six Christie Captiva 1DLP® laser phosphor projectors, which set the stage for visitors entering the exhibition by providing an immersive space that reminds them that the world is not as it seems. Produced by the Institute for Quantum Computing at the University of Waterloo, QUANTUM has been selected as a Signature Initiative of the Government of Canada’s sesquicentennial celebrations. QUANTUM is part of Innovation150, a partnership of five leading science outreach organizations leading a cross-country celebration of science and innovation with stops at Science World at TELUS World of Science in Vancouver and the Discovery Centre in Halifax. “Quantum science is transforming our understanding of the world around us,” says Tobi Day-Hamilton, associate director at the Institute for Quantum Computing. “Christie technology is helping us share the wonders of the quantum world in new and innovative ways and I’m delighted to partner with them on this incredible experience.” “We’re pleased that Christie projection technology will be a part of bringing quantum science to life – not only at THEMUSEUM, but at science centres across Canada,” says Kathryn Cress, vice president, Global & Corporate Marketing, Christie. “The fusion of technology and science in QUANTUM is truly representative of the Kitchener-Waterloo region, and we’re thrilled that the rest of Canada will have the opportunity to experience this exhibit first-hand.” About Christie Christie Digital Systems Canada Inc. is a global visual and audio technologies company and is a wholly-owned subsidiary of Ushio, Inc., Japan, (JP:6925). Consistently setting the standards by being the first to market some of the world’s most advanced projectors and complete system displays, Christie is recognized as one of the most innovative visual technology companies in the world. From retail displays to Hollywood, mission critical command centers to classrooms and training simulators, Christie display solutions and projectors capture the attention of audiences around the world with dynamic and stunning images. Visit http://www.christiedigital.com. “Christie” is a trademark of Christie Digital Systems USA, Inc., registered in the United States of America and certain other countries. DLP® is a registered trademark of Texas Instruments
Serbyn M.,Massachusetts Institute of Technology |
Papic Z.,Princeton University |
Abanin D.A.,Perimeter Institute for Theoretical Physics |
Abanin D.A.,Institute for Quantum Computing
Physical Review Letters | Year: 2013
We construct a complete set of local integrals of motion that characterize the many-body localized (MBL) phase. Our approach relies on the assumption that local perturbations act locally on the eigenstates in the MBL phase, which is supported by numerical simulations of the random-field XXZ spin chain. We describe the structure of the eigenstates in the MBL phase and discuss the implications of local conservation laws for its nonequilibrium quantum dynamics. We argue that the many-body localization can be used to protect coherence in the system by suppressing relaxation between eigenstates with different local integrals of motion. © 2013 American Physical Society.
Serbyn M.,Massachusetts Institute of Technology |
Papic Z.,Princeton University |
Abanin D.A.,Perimeter Institute for Theoretical Physics |
Abanin D.A.,Institute for Quantum Computing
Physical Review Letters | Year: 2013
Recent numerical work by Bardarson, Pollmann, and Moore revealed a slow, logarithmic in time, growth of the entanglement entropy for initial product states in a putative many-body localized phase. We show that this surprising phenomenon results from the dephasing due to exponentially small interaction-induced corrections to the eigenenergies of different states. For weak interactions, we find that the entanglement entropy grows as ξln (Vt/), where V is the interaction strength, and ξ is the single-particle localization length. The saturated value of the entanglement entropy at long times is determined by the participation ratios of the initial state over the eigenstates of the subsystem. Our work shows that the logarithmic entanglement growth is a universal phenomenon characteristic of the many-body localized phase in any number of spatial dimensions, and reveals a broad hierarchy of dephasing time scales present in such a phase. © 2013 American Physical Society.