12 research outputs found
Microwave cavity light shining through a wall optimization and experiment
It has been proposed that microwave cavities can be used in a photon
regeneration experiment to search for hidden sector photons. Using two isolated
cavities, the presence of hidden sector photons could be inferred from a 'light
shining through a wall' phenomenon. The sensitivity of the experiment has
strong a dependence on the geometric construction and electromagnetic mode
properties of the two cavities. In this paper we perform an in depth
investigation to determine the optimal setup for such an experiment. We also
describe the results of our first microwave cavity experiment to search for
hidden sector photons. The experiment consisted of two cylindrical copper
cavities stacked axially inside a single vacuum chamber. At a hidden sector
photon mass of 37.78 micro eV we place an upper limit on the kinetic mixing
parameter chi = 2.9 * 10^(-5). Whilst this result lies within already
established limits our experiment validates the microwave cavity `light shining
through a wall' concept. We also show that the experiment has great scope for
improvement, potentially able to reduce the current upper limit on the mixing
parameter chi by several orders of magnitude.Comment: To be published in PR
Microwave cavity hidden sector photon threshold crossing
Hidden sector photons are a weakly interacting slim particle arising from an
additional U(1) gauge symmetry predicted by many standard model extensions. We
present and demonstrate a new experimental method using a single microwave
cavity to search for hidden sector photons. Only photons with a great enough
energy are able to oscillate into hidden sector photons of a particular mass.
If our cavity is driven on resonance and tuned over the corresponding threshold
frequency, there is an observable drop in the circulating power signifying the
creation of hidden sector photons. This approach avoids the problems of
microwave leakage and frequency matching inherent in photon regeneration
techniques
Two-dimensional optomechanical crystal resonator in gallium arsenide
In the field of quantum computation and communication there is a compelling
need for quantum-coherent frequency conversion between microwave electronics
and infra-red optics. A promising platform for this is an optomechanical
crystal resonator that uses simultaneous photonic and phononic crystals to
create a co-localized cavity coupling an electromagnetic mode to an acoustic
mode, which then via electromechanical interactions can undergo direct
transduction to electronics. The majority of work in this area has been on
one-dimensional nanobeam resonators which provide strong optomechanical
couplings but, due to their geometry, suffer from an inability to dissipate
heat produced by the laser pumping required for operation. Recently, a
quasi-two-dimensional optomechanical crystal cavity was developed in silicon
exhibiting similarly strong coupling with better thermalization, but at a
mechanical frequency above optimal qubit operating frequencies. Here we adapt
this design to gallium arsenide, a natural thin-film single-crystal
piezoelectric that can incorporate electromechanical interactions, obtaining a
mechanical resonant mode at f_m ~ 4.5 GHz ideal for superconducting qubits, and
demonstrating optomechanical coupling g_om/(2pi) ~ 650 kHz
Bidirectional multi-photon communication between remote superconducting nodes
Quantum communication testbeds provide a useful resource for experimentally
investigating a variety of communication protocols. Here we demonstrate a
superconducting circuit testbed with bidirectional multi-photon state transfer
capability using time-domain shaped wavepackets. The system we use to achieve
this comprises two remote nodes, each including a tunable superconducting
transmon qubit and a tunable microwave-frequency resonator, linked by a 2
m-long superconducting coplanar waveguide, which serves as a transmission line.
We transfer both individual and superposition Fock states between the two
remote nodes, and additionally show that this bidirectional state transfer can
be done simultaneously, as well as used to entangle elements in the two nodes.Comment: Main Paper has 6 pages, 4 figures. Supplementary has 14 pages, 16
figures, 2 table
Quantum erasure using entangled surface acoustic phonons
Using the deterministic, on-demand generation of two entangled phonons, we
demonstrate a quantum eraser protocol in a phononic interferometer where the
which-path information can be heralded during the interference process.
Omitting the heralding step yields a clear interference pattern in the
interfering half-quanta pathways; including the heralding step suppresses this
pattern. If we erase the heralded information after the interference has been
measured, the interference pattern is recovered, thereby implementing a
delayed-choice quantum erasure. The test is implemented using a closed
surface-acoustic-wave communication channel into which one superconducting
qubit can emit itinerant phonons that the same or a second qubit can later
re-capture. If the first qubit releases only half of a phonon, the system
follows a superposition of paths during the phonon propagation: either an
itinerant phonon is in the channel, or the first qubit remains in its excited
state. These two paths are made to constructively or destructively interfere by
changing the relative phase of the two intermediate states, resulting in a
phase-dependent modulation of the first qubit's final state, following
interaction with the half-phonon. A heralding mechanism is added to this
construct, entangling a heralding phonon with the signalling phonon. The first
qubit emits a phonon herald conditioned on the qubit being in its excited
state, with no signaling phonon, and the second qubit catches this heralding
phonon, storing which-path information which can either be read out, destroying
the signaling phonon's self-interference, or erased.Comment: 16 pages, 8 figure
Developing a platform for linear mechanical quantum computing
Linear optical quantum computing provides a desirable approach to quantum
computing, with a short list of required elements. The similarity between
photons and phonons points to the interesting potential for linear mechanical
quantum computing (LMQC), using phonons in place of photons. While
single-phonon sources and detectors have been demonstrated, a phononic
beamsplitter element remains an outstanding requirement. Here we demonstrate
such an element, using two superconducting qubits to fully characterize a
beamsplitter with single phonons. We further use the beamsplitter to
demonstrate two-phonon interference, a requirement for two-qubit gates,
completing the toolbox needed for LMQC. This advance brings linear quantum
computing to a fully solid-state system, along with straightforward conversion
between itinerant phonons and superconducting qubits
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Modular Quantum Processor with an All-to-All Reconfigurable Router
Superconducting qubits provide a promising approach to large-scale fault-tolerant quantum computing. However, qubit connectivity on a planar surface is typically restricted to only a few neighboring qubits. Achieving longer-range and more flexible connectivity, which is particularly appealing in light of recent developments in error-correcting codes, however, usually involves complex multilayer packaging and external cabling, which is resource intensive and can impose fidelity limitations. Here, we propose and realize a high-speed on-chip quantum processor that supports reconfigurable all-to-all coupling with a large on-off ratio. We implement the design in a four-node quantum processor, built with a modular design comprising a wiring substrate coupled to two separate qubit-bearing substrates, each including two single-qubit nodes. We use this device to demonstrate reconfigurable controlled- gates across all qubit pairs, with a benchmarked average fidelity of 96.00% ± 0.08% and best fidelity of 97.14% ± 0.07%, limited mainly by dephasing in the qubits. We also generate multiqubit entanglement, distributed across the separate modules, demonstrating GHZ-3 and GHZ-4 states with fidelities of 88.15% ± 0.24% and 75.18% ± 0.11%, respectively. This approach promises efficient scaling to larger-scale quantum circuits and offers a pathway for implementing quantum algorithms and error-correction schemes that benefit from enhanced qubit connectivity
Resonant Regeneration in the Sub-Quantum Regime -- A demonstration of fractional quantum interference
Light shining through wall experiments (in the optical as well as in the
microwave regime) are a powerful tool to search for light particles coupled
very weakly to photons such as axions or extra hidden sector photons. Resonant
regeneration, where a resonant cavity is employed to enhance the regeneration
rate of photons, is one of the most promising techniques to improve the
sensitivity of the next generation of experiments. However, doubts have been
voiced if such methods work at very low regeneration rates where on average the
cavity contains less than one photon. In this note we report on a demonstration
experiment using a microwave cavity driven with extremely low power, to show
that resonant amplification works also in this regime. In accordance with
standard quantum mechanics this is a demonstration that interference also works
at the level of less than one quantum. As an additional benefit this experiment
shows that thermal photons inside the cavity cause no adverse effects.Comment: 14 pages, 5 figure