Description:

Title: Clearly witnessing the quantum fluctuations of a mechanical oscillator

Speaker: Raymond W. Simmonds, NIST Boulder, Quantum Electronics & Photonics Division

Abstract:

Can a harmonic oscillator ever be truly at rest? It may seem strange, but according to Werner Heisenberg’s uncertainty principle, the answer is: “no!” Even at a temperature of absolute zero, in its lowest possible energy state or the “ground state of motion”, the oscillator must still exhibit quantum fluctuations of its position and momentum. But how can we unambiguously detect motion of a purely quantum origin? Oddly enough, if you were to extract energy out of the oscillator one quanta at a time, you would eventually reach the ground state and extract nothing more, leading you to conclude that the oscillator must be at rest. On the other hand, if you were to try to directly detect motion of this ground state with linear position measurements, you could be easily fooled by the addition of classical noise that could masquerade as legitimate quantum fluctuations.

In this talk, I will discuss a unique experiment that can unequivocally observe the quantum fluctuations of a mechanical oscillator near its ground state of motion. To do this, we have created a hybrid system that merges a microwave opto-mechanical element [1] with a superconducting quantum bit (or qubit) [2]. Parametric coupling between the electrical and the mechanical oscillators allows us to cool the mechanics to its ground state [3] and then amplify the intrinsic quantum fluctuations in both oscillators into real energy quanta [4] that can then be detected by the qubit, which effectively acts as an ideal single photon or phonon detector.

Operated in reverse, this system could be used to prepare complex quantum states of mechanical motion or to generate entanglement between the mechanical phonons and the electrical microwave photons [4]. Controlling the quantum states of long-lived mechanical oscillators is important for applications in quantum information and for providing new, powerful quantum-enhanced detection methods for unbeatable precision measurements.

[1] J. D. Teufel, et al., R. W. Simmonds, Nature 471, 204 (2011)

[2] R. W. Simmonds, et al., Physical Review Letters 93, 077003 (2004)

[3] J. D. Teufel, et al., K. W. Lehnert, R. W. Simmonds, Nature 475, 359 (2011)

[4] T. A. Palomaki, J. D. Teufel, R. W. Simmonds, K. W. Lehnert, Science 342, 710 (2013)

Keywords: Physics, Astronomy, CMP