Faithful conversion of propagating quantum information to mechanical motion

• Published in: Nature physics 2017-12, Vol.13 (12), p.1163-1167
• Main Authors: Reed, A. P., Mayer, K. H., Teufel, J. D., Burkhart, L. D., Pfaff, W., Reagor, M., Sletten, L., Ma, X., Schoelkopf, R. J., Knill, E., Lehnert, K. W.
• Format: Article
• Language: English
• Subjects: 639/766/1130/1064; 639/766/1130/2800; 639/766/483/481; Atomic; Classical and Continuum Physics; Coding; Complex Systems; Condensed Matter Physics; Conversion; letter; Mathematical and Computational Physics; Microprocessors; Molecular; Optical and Plasma Physics; Photons; Physics; Quantum computing; Quantum mechanics; Quantum phenomena; Quantum theory; Qubits (quantum computing); Resonators; Squeezed states (quantum theory); Superconductivity; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys4251

Combining micrometre-sized mechanical resonators with superconducting quantum circuits, quantum information encoded with photons now can be converted to the motion of a macroscopic object. The motion of micrometre-sized mechanical resonators can now be controlled and measured at the fundamental limits imposed by quantum mechanics. These resonators have been prepared in their motional ground state 1 , 2 , 3 or in squeezed states 4 , 5 , 6 , measured with quantum-limited precision 7 , and even entangled with microwave fields 8 . Such advances make it possible to process quantum information using the motion of a macroscopic object. In particular, recent experiments have combined mechanical resonators with superconducting quantum circuits to frequency-convert, store and amplify propagating microwave fields 9 , 10 , 11 , 12 . But these systems have not been used to manipulate states that encode quantum bits (qubits), which are required for quantum communication and modular quantum computation 13 , 14 . Here we demonstrate the conversion of propagating qubits encoded as superpositions of zero and one photons to the motion of a micromechanical resonator with a fidelity in excess of the classical bound. This ability is necessary for mechanical resonators to convert quantum information between the microwave and optical domains 15 , 16 , 17 or to act as storage elements in a modular quantum information processor 12 , 13 , 18 . Additionally, these results are an important step towards testing speculative notions that quantum theory may not be valid for sufficiently massive systems 19 .