A macroscopic mechanical resonator driven by mesoscopic electrical back-action

Abstract

Systems with coupled mechanical and optical or electrical degrees of freedom have fascinating dynamics that, through macroscopic manifestations of quantum behaviour, provide new insights into the transition between the classical and quantum worlds. Of particular interest is the back-action of electrons and photons on mechanical oscillators, which can lead to cooling and amplification of mechanical motion. Furthermore, feedback, which is naturally associated with back-action, has been predicted to have significant consequences for the noise of a detector coupled to a mechanical oscillator. Recently it has also been demonstrated that such feedback effects lead to strong coupling between single-electron transport and mechanical motion in carbon nanotube nanomechanical resonators. Here we present noise measurements which show that the mesoscopic back-action of electrons tunnelling through a radio-frequency quantum point contact causes driven vibrations of the host crystal. This effect is a remarkable macroscopic manifestation of microscopic quantum behaviour, where the motion of a mechanical oscillator-the host crystal, which consists of on the order of 10(20) atoms-is determined by statistical fluctuations of tunnelling electrons.

Electroluminescence and multiphoton effects in a resonator driven by a tunnel junction

“…A study of nonequilibrium effects in the resonator which is strongly coupled to a biased tunnel junction has, to the best of our knowledge, not yet been performed, although the setup may find wide applications. For instance, the system has been used as an effective charge detector for single-shot read-out of quantum-dot based qubits [18][19][20][21] , and as a displacement detector which can resolve the momentum and position of nanomechanical resonators with high precision [22][23][24][25][26] . Recently, it has been proposed that a tunnel junction can be used to generate squeezed light and microwave photon pairs 27,28 .…”

Nanomechanical resonator coupled linearly via its momentum to a quantum point contact

“…As already mentioned, the experiment of Ref. [16] is in the regime of strong tunneling, where the polaronic and Born-Markov approximations are no longer valid and scattering matrix methods can be used instead 20 -an approach we intend to investigate in future work.…”

“…[16]. It is interesting to know if the simultaneous interaction of the oscillator with the position-coupled external bath and the momentum-coupled detector bath can put the oscillator into a so-called squeezed state -a clear signature of quantum behavior in the system.…”

“…II below), can be described by a momentum-coupled effective Hamiltonian, was studied experimentally by Stettenheim et al 16 Their experiment involved a nanomechanical GaAs oscillator coupled piezoelectrically to a radio-frequency QPC embedded in it. Measurements of the current noise through the QPC detector showed that the quantum statistical fluctuations of tunneling electrons could affect the macroscopic dynamics of the host crystal.…”

“…1(a) (reproduced from Ref. [16]) shows the GaAs crystal containing a two-dimensional electron gas (2DEG). A displacement dy of the front and back faces of the crystal leads to a compression dz at the midpoint of the left face and a corresponding expansion dz at the midpoint of the right face, as shown.…”