17 research outputs found
Quantum state preparation, tomography, and entanglement of mechanical oscillators
Precisely engineered mechanical oscillators keep time, filter signals, and
sense motion, making them an indispensable part of today's technological
landscape. These unique capabilities motivate bringing mechanical devices into
the quantum domain by interfacing them with engineered quantum circuits.
Proposals to combine microwave-frequency mechanical resonators with
superconducting devices suggest the possibility of powerful quantum acoustic
processors. Meanwhile, experiments in several mechanical systems have
demonstrated quantum state control and readout, phonon number resolution, and
phonon-mediated qubit-qubit interactions. Currently, these acoustic platforms
lack processors capable of controlling multiple mechanical oscillators' quantum
states with a single qubit, and the rapid quantum non-demolition measurements
of mechanical states needed for error correction. Here we use a superconducting
qubit to control and read out the quantum state of a pair of nanomechanical
resonators. Our device is capable of fast qubit-mechanics swap operations,
which we use to deterministically manipulate the mechanical states. By placing
the qubit into the strong dispersive regime with both mechanical resonators
simultaneously, we determine the resonators' phonon number distributions via
Ramsey measurements. Finally, we present quantum tomography of the prepared
nonclassical and entangled mechanical states. Our result represents a concrete
step toward feedback-based operation of a quantum acoustic processor.Comment: 13 pages, 4+5 figure
Coupling a superconducting quantum circuit to a phononic crystal defect cavity
Connecting nanoscale mechanical resonators to microwave quantum circuits
opens new avenues for storing, processing, and transmitting quantum
information. In this work, we couple a phononic crystal cavity to a tunable
superconducting quantum circuit. By fabricating a one-dimensional periodic
pattern in a thin film of lithium niobate and introducing a defect in this
artificial lattice, we localize a 6 gigahertz acoustic resonance to a
wavelength-scale volume of less than one cubic micron. The strong
piezoelectricity of lithium niobate efficiently couples the localized
vibrations to the electric field of a widely tunable high-impedance Josephson
junction array resonator. We measure a direct phonon-photon coupling rate
and a mechanical quality factor
leading to a cooperativity when
the two modes are tuned into resonance. Our work has direct application to
engineering hybrid quantum systems for microwave-to-optical conversion as well
as emerging architectures for quantum information processing.Comment: 9 pages, 7 figure
Quantum dynamics of a few-photon parametric oscillator
Modulating the frequency of a harmonic oscillator at nearly twice its natural
frequency leads to amplification and self-oscillation. Above the oscillation
threshold, the field settles into a coherent oscillating state with a
well-defined phase of either or . We demonstrate a quantum parametric
oscillator operating at microwave frequencies and drive it into oscillating
states containing only a few photons. The small number of photons present in
the system and the coherent nature of the nonlinearity prevents the environment
from learning the randomly chosen phase of the oscillator. This allows the
system to oscillate briefly in a quantum superposition of both phases at once -
effectively generating a nonclassical Schr\"{o}dinger's cat state. We
characterize the dynamics and states of the system by analyzing the output
field emitted by the oscillator and implementing quantum state tomography
suited for nonlinear resonators. By demonstrating a quantum parametric
oscillator and the requisite techniques for characterizing its quantum state,
we set the groundwork for new schemes of quantum and classical information
processing and extend the reach of these ubiquitous devices deep into the
quantum regime
A silicon-organic hybrid platform for quantum microwave-to-optical transduction
Low-loss fiber optic links have the potential to connect superconducting quantum processors together over long distances to form large scale quantum networks. A key component of these future networks is a quantum transducer that coherently and bidirectionally converts photons from microwave frequencies to optical frequencies. We present a platform for electro-optic photon conversion based on silicon-organic hybrid photonics. Our device combines high quality factor microwave and optical resonators with an electro-optic polymer cladding to perform microwave-to-optical photon conversion from 6.7 GHz to 193 THz (1558 nm). The device achieves an electro-optic coupling rate of 590 Hz in a millikelvin dilution refrigerator environment. We use an optical heterodyne measurement technique to demonstrate the single-sideband nature of the conversion with a selectivity of approximately 10 dB. We analyze the effects of stray light in our device and suggest ways in which this can be mitigated. Finally, we present initial results on high-impedance spiral resonators designed to increase the electro-optic coupling