Abstract
We investigate theoretically the dynamics of two quasidegenerate mechanical modes coupled through an open quantum two-level system. A mean-field approach shows that by engineering the retarded response of the two-level system with a coherent drive, the non-Hermitian mechanical spectrum exhibits an exceptional degeneracy point where the two modes coalesce. We show that this degeneracy can be exploited to manipulate the vectorial polarization of the mechanical oscillations. We find that adiabatically varying the detuning and the intensity of the drive induces a rotation of the mechanical polarization, which enables the topological and chiral actuation of one mode from the other. This topological manifestation of the degeneracy is further supported by quantum-jump Monte Carlo simulations to account for the strong quantum fluctuations due to the spontaneous emission of the two-level system. Our presentation focuses on a promising realization based on flexural modes of a carbon-nanotube cantilever coupled to a single-molecule electric dipole irradiated by a laser.
Highlights
The manipulation and detection of nanometer oscillators are important challenges in nanomechanics [1,2,3], and recent progress has led to unprecedented high-resolution sensors [4,5,6,7,8,9]
We show that by adiabatically varying, along a closed path, the frequency and the intensity of a coherent field driving a Two-level systems (TLSs) coupled to two quasidegenerate mechanical modes, it is possible to induce a change in the state of the mechanical oscillator that depends on the topology of the path
We come to the main question we want to address with the simulations: does the exceptional points (EPs) remain stable in the presence of fluctuations and backaction? To test the mean-field manifestation of the EP, we study the evolution of the mechanical mode 1 or 2 with initial amplitude 10xzpf and ramp adiabatically δ from 0 to −8 over the timescale T = 104/ for various values of
Summary
The manipulation and detection of nanometer oscillators are important challenges in nanomechanics [1,2,3], and recent progress has led to unprecedented high-resolution sensors [4,5,6,7,8,9]. We show that by adiabatically varying, along a closed path, the frequency and the intensity of a coherent field driving a TLS coupled to two quasidegenerate mechanical modes, it is possible to induce a change in the state of the mechanical oscillator that depends on the topology of the path. We show that this behavior is due to the presence of an EP in the mean-field description of the electromechanical spectrum.
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