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Taylor J.M.,Joint Quantum Institute NIST | Sorensen A.S.,Copenhagen University | Marcus C.M.,Harvard University | Polzik E.S.,Copenhagen University
Physical Review Letters | Year: 2011

We explore a method for laser cooling and optical detection of excitations in a room temperature LC electrical circuit. Our approach uses a nanomechanical oscillator as a transducer between optical and electronic excitations. An experimentally feasible system with the oscillator capacitively coupled to the LC and at the same time interacting with light via an optomechanical force is shown to provide strong electromechanical coupling. Conditions for improved sensitivity and quantum limited readout of electrical signals with such an "optical loud speaker" are outlined. © 2011 American Physical Society.

Medford J.,Harvard University | Beil J.,Harvard University | Beil J.,Copenhagen University | Taylor J.M.,Joint Quantum Institute NIST | And 9 more authors.
Nature Nanotechnology | Year: 2013

Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes. © 2013 Macmillan Publishers Limited.

Kielpinski D.,Griffith University | Kafri D.,Joint Quantum Institute NIST | Woolley M.J.,University of Queensland | Milburn G.J.,University of Queensland | Taylor J.M.,Joint Quantum Institute NIST
Physical Review Letters | Year: 2012

We show how to bridge the divide between atomic systems and electronic devices by engineering a coupling between the motion of a single ion and the quantized electric field of a resonant circuit. Our method can be used to couple the internal state of an ion to the quantized circuit with the same speed as the internal-state coupling between two ions. All the well-known quantum information protocols linking ion internal and motional states can be converted to protocols between circuit photons and ion internal states. Our results enable quantum interfaces between solid state qubits, atomic qubits, and light, and lay the groundwork for a direct quantum connection between electrical and atomic metrology standards. © 2012 American Physical Society.

Medford J.,Harvard University | Beil J.,Copenhagen University | Taylor J.M.,Joint Quantum Institute NIST | Rashba E.I.,Harvard University | And 3 more authors.
Physical Review Letters | Year: 2013

We introduce a solid-state qubit in which exchange interactions among confined electrons provide both the static longitudinal field and the oscillatory transverse field, allowing rapid and full qubit control via rf gate-voltage pulses. We demonstrate two-axis control at a detuning sweet spot, where leakage due to hyperfine coupling is suppressed by the large exchange gap. A π/2-gate time of 2.5 ns and a coherence time of 19 μs, using multipulse echo, are also demonstrated. Model calculations that include effects of hyperfine noise are in excellent quantitative agreement with experiment. © 2013 American Physical Society.

Bagci T.,Copenhagen University | Simonsen A.,Copenhagen University | Schmid S.,Technical University of Denmark | Villanueva L.G.,Technical University of Denmark | And 7 more authors.
Frontiers in Optics, FiO 2014 | Year: 2014

Electronic signals are converted with high efficiency, and very low added noise, to the optical domain by coupling them to a nanomechanical membrane whose displacement is interferometrically monitored with quantum-limited sensitivity.

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