Quantum Oscillator Noise Spectroscopy via Displaced Cat States

Abstract

Quantum harmonic oscillators are central to many modern quantum technologies. We introduce a method to determine the frequency noise spectrum of oscillator modes through coupling them to a qubit with continuously driven qubit-state-dependent displacements. We reconstruct the noise spectrum using a series of different drive phase and amplitude modulation patterns in conjunction with a data-fusion routine based on convex optimization. We apply the technique to the identification of intrinsic noise in the motional frequency of a single trapped ion with sensitivity to fluctuations at the sub-Hz level in a spectral range from quasi-dc up to 50 kHz.

Engineering dynamical couplings for quantum thermodynamic tasks

“…The intriguing question here is whether the simultaneous achievement of the three desiderata of a heat engine (efficiency close to the Carnot efficiency, high output power and constancy of the power output) is possible also for standard heat engines operating with two or more heat baths at different temperatures. Further generalizations of our approach could be obtained by considering a more complex working medium [17,[94][95][96][97][98], like coupled oscillators and, with a considerably higher numerical effort, nonlinear oscillators and qubit systems.…”

Building and characterizing a stylus ion-trap system

“…[13] We have noticed recent efforts exploring the detection of noise spectra using harmonic oscillators. [14][15][16] The basic ideas in these works are enacted on the laser-cooled trapped ions prepared in vibrational ground state and varied with resonance frequencies. With these singleion sensors, the intrinsic noise spectra of the ion-trap potentials were experimentally identified and demonstrated.…”

Quantum Vector Signal Analyzer

“…As V q is increased, the quadrupole tones generate a squeezing interaction intrinsic to the QVSA Hamiltonian which creates an intrinsically phasesqueezed state; this will be the subject of future work. With these modifications, a single trapped 9 Be + ion in the trap of Ref. [23], with a secular frequency stability of ∼ 10 Hz, prepared in an r = 2.2 squeezed state [5], and with the use of a pre-amplifier e.g.…”