Abstract
Hybrid quantum optomechanical systems1 interface a macroscopic mechanical degree of freedom with a single two-level system such as a single spin2-4, a superconducting qubit5-7 or a single optical emitter8-12. Recently, hybrid systems operating in the microwave domain have witnessed impressive progress13,14. Concurrently, only a few experimental approaches have successfully addressed hybrid systems in the optical domain, demonstrating that macroscopic motion can modulate the two-level system transition energy9,10,15. However, the reciprocal effect, corresponding to the backaction of a single quantum system on a macroscopic mechanical resonator, has remained elusive. In contrast to an optical cavity, a two-level system operates with no more than a single energy quantum. Hence, it requires a much stronger hybrid coupling rate compared to cavity optomechanical systems1,16. Here, we build on the large strain coupling between an oscillating microwire and a single embedded quantum dot9. We resonantly drive the quantum dot's exciton using a laser modulated at the mechanical frequency. State-dependent strain then results in a time-dependent mechanical force that actuates microwire motion. This force is almost three orders of magnitude larger than the radiation pressure produced by the photon flux interacting with the quantum dot. In principle, the state-dependent force could constitute a strategy to coherently encode the quantum dot quantum state onto a mechanical degree of freedom1.
Highlights
Wherehω0 is the quantum dot (QD) transition energy for the wire at rest ( ̄hω0 1.35 eV, wavelength 920 nm), and σz = |e e| − |g g| is the Pauli operator describing the population of the QD states
The rest position xe of the mechanical oscillator for the excited QD is different from the rest position xg for the empty QD
As a consequence, when the QD is in the ground state and is optically brought in the excited state on a time scale much faster that 2π/Ωm, the QD induces on the wire a static force
Summary
The QD fluorescence (wavelength around 920 nm) is detected by a photon counting avalanche photodiode at the output of a 1.5 m focal length spectrometer equipped with a 1200 grooves/mm grating (resolution 12 μeV). From the QD line shift when the laser is "on", the temperature increase caused by light absorption has been estimated to be less than 0.01K This QD independent driven motion has a root mean square amplitude of xP T = 50 pm and features a phase delay ΦP T = −36 ± 5◦ with respect to a motion that would respond instantaneously to the excitation laser modulation. This phase delay is well accounted for by estimating the thermal time response of the wire (see SI). The PLL in-loop frequency signal is used to infer the total motion phase shift (see below and SI)
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