Abstract
We propose a scheme involving a Cooper pair transistor (CPT) embedded in a superconducting microwave cavity, where the CPT serves as a charge tunable quantum inductor to facilitate ultra-strong coupling between photons in the cavity and a nano- to meso-scale mechanical resonator. The mechanical resonator is capacitively coupled to the CPT, such that mechanical displacements of the resonator cause a shift in the CPT inductance and hence the cavity's resonant frequency. The amplification provided by the CPT is sufficient for the zero point motion of the mechanical resonator alone to cause a significant change in the cavity resonance. Conversely, a single photon in the cavity causes a shift in the mechanical resonator position on the order of its zero point motion. As a result, the cavity-Cooper pair transistor coupled to a mechanical resonator will be able to access a regime in which single photons can affect single phonons and vice versa. Realizing this ultra-strong coupling regime will facilitate the creation of non-classical states of the mechanical resonator, as well as the means to accurately characterize such states by measuring the cavity photon field.
Highlights
There is presently intense worldwide interest in the application of quantum mechanical phenomena to communications, information processing, and precision measurement
Practitioners of the above fields are keenly interested in the boundary between quantum mechanical and classical behavior, and in the ways in which quantum behavior can be extended into regimes that at first glance might seem to lie in the province of classical mechanics [1, 2]
We describe an optomechanical scheme involving a Cooper pair transistor (CPT) that is embedded in a superconducting microwave cavity, where a mechanically compliant, biased gate electrode couples mechanical motion to the cavity via the CPT
Summary
There is presently intense worldwide interest in the application of quantum mechanical phenomena to communications, information processing, and precision measurement. The parameter g is the vacuum optomechanical 0 coupling strength, and expresses the shift in cavity frequency due to displacement of the mechanical resonator by its zero point length xzp =. The shift in cavity frequency due to a single phonon must be larger than the linewidth κ = ω0 Q, where Q is the cavity mode quality factor; this is equivalent to requiring that the ratio g κ, called the granularity parameter, be greater than one [8]. Shown for comparison are the estimated parameters of the cCPT-mechanical resonator scheme discussed in the present work. We describe an optomechanical scheme involving a Cooper pair transistor (CPT) that is embedded in a superconducting microwave cavity, where a mechanically compliant, biased gate electrode couples mechanical motion to the cavity via the CPT.
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