1,358 research outputs found
From Cavity Electromechanics to Cavity Optomechanics
We present an overview of experimental work to embed high-Q mesoscopic
mechanical oscillators in microwave and optical cavities. Based upon recent
progress, the prospect for a broad field of "cavity quantum mechanics" is very
real. These systems introduce mesoscopic mechanical oscillators as a new
quantum resource and also inherently couple their motion to photons throughout
the electromagnetic spectrum.Comment: 8 pages, 6 figures, ICAP proceedings submissio
Coupled multimode optomechanics in the microwave regime
The motion of micro- and nanomechanical resonators can be coupled to
electromagnetic fields. This allows to explore the mutual interaction and
introduces new means to manipulate and control both light and mechanical
motion. Such optomechanical systems have recently been implemented in
nanoelectromechanical systems involving a nanomechanical beam coupled to a
superconducting microwave resonator. Here, we propose optomechanical systems
that involve multiple, coupled microwave resonators. In contrast to similar
systems in the optical realm, the coupling frequency governing photon exchange
between microwave modes is naturally comparable to typical mechanical
frequencies. For instance this enables new ways to manipulate the microwave
field, such as mechanically driving coherent photon dynamics between different
modes. In particular we investigate two setups where the electromagnetic field
is coupled either linearly or quadratically to the displacement of a
nanomechanical beam. The latter scheme allows to perform QND Fock state
detection. For experimentally realistic parameters we predict the possibility
to measure an individual quantum jump from the mechanical ground state to the
first excited state.Comment: 6 pages, 4 figures, 1 tabl
Effective non-adiabatic Hamiltonians for the quantum nuclear motion over coupled electronic states
The quantum mechanical motion of the atomic nuclei is considered over a
single- or a multi-dimensional subspace of electronic states which is separated
by a gap from the rest of the electronic spectrum over the relevant range of
nuclear configurations. The electron-nucleus Hamiltonian is block-diagonalized
up to through a unitary transformation of the
electronic subspace and the corresponding th-order effective Hamiltonian is
derived for the quantum nuclear motion. Explicit but general formulae are given
for the second- and the third-order corrections. As a special case, the
second-order Hamiltonian corresponding to an isolated electronic state is
recovered which contains the coordinate-dependent mass-correction terms in the
nuclear kinetic energy operator. For a multi-dimensional, explicitly coupled
electronic band, the second-order Hamiltonian contains the usual BO terms and
non-adiabatic corrections but generalized mass-correction terms appear as well.
These, earlier neglected terms, perturbatively account for the outlying
(discrete and continuous) electronic states not included in the explicitly
coupled electronic subspace
Demonstration of efficient nonreciprocity in a microwave optomechanical circuit
The ability to engineer nonreciprocal interactions is an essential tool in
modern communication technology as well as a powerful resource for building
quantum networks. Aside from large reverse isolation, a nonreciprocal device
suitable for applications must also have high efficiency (low insertion loss)
and low output noise. Recent theoretical and experimental studies have shown
that nonreciprocal behavior can be achieved in optomechanical systems, but
performance in these last two attributes has been limited. Here we demonstrate
an efficient, frequency-converting microwave isolator based on the
optomechanical interactions between electromagnetic fields and a mechanically
compliant vacuum gap capacitor. We achieve simultaneous reverse isolation of
more than 20 dB and insertion loss less than 1.5 dB over a bandwidth of 5 kHz.
We characterize the nonreciprocal noise performance of the device, observing
that the residual thermal noise from the mechanical environments is routed
solely to the input of the isolator. Our measurements show quantitative
agreement with a general coupled-mode theory. Unlike conventional isolators and
circulators, these compact nonreciprocal devices do not require a static
magnetic field, and they allow for dynamic control of the direction of
isolation. With these advantages, similar devices could enable programmable,
high-efficiency connections between disparate nodes of quantum networks, even
efficiently bridging the microwave and optical domains.Comment: 9 pages, 6 figure
High Fidelity Adiabatic Quantum Computation via Dynamical Decoupling
We introduce high-order dynamical decoupling strategies for open system
adiabatic quantum computation. Our numerical results demonstrate that a
judicious choice of high-order dynamical decoupling method, in conjunction with
an encoding which allows computation to proceed alongside decoupling, can
dramatically enhance the fidelity of adiabatic quantum computation in spite of
decoherence.Comment: 5 pages, 4 figure
Effective dynamics for particles coupled to a quantized scalar field
We consider a system of N non-relativistic spinless quantum particles
(``electrons'') interacting with a quantized scalar Bose field (whose
excitations we call ``photons''). We examine the case when the velocity v of
the electrons is small with respect to the one of the photons, denoted by c
(v/c= epsilon << 1). We show that dressed particle states exist (particles
surrounded by ``virtual photons''), which, up to terms of order (v/c)^3, follow
Hamiltonian dynamics. The effective N-particle Hamiltonian contains the kinetic
energies of the particles and Coulomb-like pair potentials at order (v/c)^0 and
the velocity dependent Darwin interaction and a mass renormalization at order
(v/c)^{2}. Beyond that order the effective dynamics are expected to be
dissipative.
The main mathematical tool we use is adiabatic perturbation theory. However,
in the present case there is no eigenvalue which is separated by a gap from the
rest of the spectrum, but its role is taken by the bottom of the absolutely
continuous spectrum, which is not an eigenvalue.
Nevertheless we construct approximate dressed electrons subspaces, which are
adiabatically invariant for the dynamics up to order (v/c)\sqrt{\ln
(v/c)^{-1}}. We also give an explicit expression for the non adiabatic
transitions corresponding to emission of free photons. For the radiated energy
we obtain the quantum analogue of the Larmor formula of classical
electrodynamics.Comment: 67 pages, 2 figures, version accepted for publication in
Communications in Mathematical Physic
Prospects for cooling nanomechanical motion by coupling to a superconducting microwave resonator
Recent theoretical work has shown that radiation pressure effects can in
principle cool a mechanical degree of freedom to its ground state. In this
paper, we apply this theory to our realization of an opto-mechanical system in
which the motion of mechanical oscillator modulates the resonance frequency of
a superconducting microwave circuit. We present experimental data demonstrating
the large mechanical quality factors possible with metallic, nanomechanical
beams at 20 mK. Further measurements also show damping and cooling effects on
the mechanical oscillator due to the microwave radiation field. These data
motivate the prospects for employing this dynamical backaction technique to
cool a mechanical mode entirely to its quantum ground state.Comment: 6 pages, 6 figure
State Transfer Between a Mechanical Oscillator and Microwave Fields in the Quantum Regime
Recently, macroscopic mechanical oscillators have been coaxed into a regime
of quantum behavior, by direct refrigeration [1] or a combination of
refrigeration and laser-like cooling [2, 3]. This exciting result has
encouraged notions that mechanical oscillators may perform useful functions in
the processing of quantum information with superconducting circuits [1, 4-7],
either by serving as a quantum memory for the ephemeral state of a microwave
field or by providing a quantum interface between otherwise incompatible
systems [8, 9]. As yet, the transfer of an itinerant state or propagating mode
of a microwave field to and from a mechanical oscillator has not been
demonstrated owing to the inability to agilely turn on and off the interaction
between microwave electricity and mechanical motion. Here we demonstrate that
the state of an itinerant microwave field can be coherently transferred into,
stored in, and retrieved from a mechanical oscillator with amplitudes at the
single quanta level. Crucially, the time to capture and to retrieve the
microwave state is shorter than the quantum state lifetime of the mechanical
oscillator. In this quantum regime, the mechanical oscillator can both store
and transduce quantum information
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