Journal Article

Coherent state transfer between itinerant microwave fields and a mechanical oscillator

Lehnert, K. W., Teufel, J. D., Simmonds, R. W., Palomaki, T. A., Harlow, J. W.

2013

Overview

The state of an itinerant microwave field can be coherently transferred into, stored in and retrieved from a mechanical oscillator with amplitudes at the single-quantum level, and the time to capture and retrieve the microwave state is shorter than the quantum state lifetime of the mechanical oscillator. Mechanical oscillation and quantum state storage In the last decade it has become possible to control macroscopic mechanical oscillators in such a way that they show quantum behaviour. The next step is to exploit this capability to produce useful devices for quantum information applications, in particular as storage elements for quantum states, a role for which mechanical oscillators show promise. One way of achieving this is to embed mechanical oscillators in superconducting circuits where quantum information can be processed in the form of microwave fields. Tauno Palomaki et al . now reach an important goal in this area by showing that the state of a microwave field can be coherently stored in and retrieved from a mechanical oscillator at the single-quantum level. Macroscopic mechanical oscillators have been coaxed into a regime of quantum behaviour by direct refrigeration 1 or a combination of refrigeration and laser-like cooling 2 , 3 . This result supports the idea that mechanical oscillators may perform useful functions in the processing of quantum information with superconducting circuits 4 , 5 , 6 , 7 , either by serving as a quantum memory for the ephemeral state of a microwave field or by providing a quantum interface between otherwise incompatible systems 8 , 9 , 10 , 11 , 12 , 13 , 14 . As yet, the transfer of an itinerant state or a propagating mode of a microwave field to and from a storage medium has not been demonstrated, owing to the inability to turn on and off the interaction between the microwave field and the medium sufficiently quickly. Here we demonstrate that the state of an itinerant microwave field can be coherently transferred into, stored in and retrieved from a mechanical oscillator with amplitudes at the single-quantum level. Crucially, the time to capture and to retrieve the microwave state is shorter than the quantum state lifetime of the mechanical oscillator. In this quantum regime, the mechanical oscillator can both store quantum information and enable its transfer between otherwise incompatible systems.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/766/483/481 / Classical and quantum physics: mechanics and fields / Electric circuit analysis / Entropy / Equipment and supplies / Evolution / Exact sciences and technology / Expected values / Fundamental areas of phenomenology (including applications) / Humanities and Social Sciences / letter / Lifetime / Methods / Microwave measurements / Microwave oscillators / multidisciplinary / Nonclassical field states; squeezed, antibunched and sub-poissonian states; operational definitions of the phase of the field; phase measurements / Optics / Oscillators / Physics / Quantum information / Quantum optics / Quantum theory / Refrigeration / Resonators / Science