505 research outputs found
Robustness of entanglement in Hawking radiation for optical systems immersed in thermal baths
Entanglement is the quantum signature of Hawking's particle pair-creation
from causal horizons, for gravitational and analog systems alike. Ambient
thermal fluctuations, ubiquitous in realistic situations, strongly affects the
entanglement generated in the Hawking process, completely extinguishing it when
the ambient temperature is comparable to the Hawking temperature. In this work,
we show that optical analog systems have a built-in robustness to thermal
fluctuations which are at rest in the laboratory. In such systems, horizons
move relative to the laboratory frame at velocities close to the speed of
light. We find that a subtle interplay between this relative velocity and
dispersion protects the Hawking-generated entanglement -- allowing ambient
temperatures several orders of magnitude larger than the Hawking temperature
without significantly affecting entanglement.Comment: 13 + 3 pages, 5 figures. Comments and questions welcom
Symplectic circuits, entanglement, and stimulated Hawking radiation in analog gravity
We introduce a convenient set of analytical tools (the Gaussian formalism)
and diagrams (symplectic circuits) to analyze multi-mode scattering events in
analog gravity, such as pair-creation a l\'a Hawking by black hole and white
hole analog event horizons. The diagrams prove to be valuable ansatzes for the
scattering dynamics, especially in settings where direct analytic results are
not straightforward and one must instead rely on numerical simulations. We use
these tools to investigate entanglement generation in single- and multi-horizon
scenarios, in particular when the Hawking process is stimulated with classical
(e.g., thermal noise) and non-classical (e.g., single-mode squeezed vacuum)
input states -- demonstrating, for instance, that initial squeezing can enhance
the production of entanglement and overcome the deleterious effects that
initial thermal fluctuations have on the output entanglement. To make further
contact with practical matters, we examine how attenuation degrades quantum
correlations between Hawking pairs. The techniques that we employ are generally
applicable to analog gravity setups of (Gaussian) bosonic quantum systems, such
as analog horizons produced in optical analogs and in Bose-Einstein
condensates, and should be of great utility in these domains. We show the
applicability of these techniques by putting them in action for an optical
system containing a pair white-black hole analog, extending our previous
analysis of [Phys. Rev. Lett. 128, 091301 (2022)].Comment: 25 + 10 pages and 21 figures. Comments welcom
Advances in Bosonic Quantum Error Correction with Gottesman-Kitaev-Preskill Codes: Theory, Engineering and Applications
Encoding quantum information into a set of harmonic oscillators is considered
a hardware efficient approach to mitigate noise for reliable quantum
information processing. Various codes have been proposed to encode a qubit into
an oscillator -- including cat codes, binomial codes and
Gottesman-Kitaev-Preskill (GKP) codes. These bosonic codes are among the first
to reach a break-even point for quantum error correction. Furthermore, GKP
states not only enable close-to-optimal quantum communication rates in bosonic
channels, but also allow for error correction of an oscillator into many
oscillators. This review focuses on the basic working mechanism, performance
characterization, and the many applications of GKP codes, with emphasis on
recent experimental progress in superconducting circuit architectures and
theoretical progress in multimode GKP qubit codes and
oscillators-to-oscillators (O2O) codes. We begin with a preliminary
continuous-variable formalism needed for bosonic codes. We then proceed to the
quantum engineering involved to physically realize GKP states. We take a deep
dive into GKP stabilization and preparation in superconducting architectures
and examine proposals for realizing GKP states in the optical domain (along
with a concise review of GKP realization in trapped-ion platforms). Finally, we
present multimode GKP qubits and GKP-O2O codes, examine code performance and
discuss applications of GKP codes in quantum information processing tasks such
as computing, communication, and sensing.Comment: 77+5 pages, 31 figures. Minor bugs fixed in v2. comments are welcome
Optimal encoding of oscillators into more oscillators
Bosonic encoding of quantum information into harmonic oscillators is a hardware efficient approach to battle noise. In this regard, oscillator-to-oscillator codes not only provide an additional opportunity in bosonic encoding, but also extend the applicability of error correction to continuous-variable states ubiquitous in quantum sensing and communication. In this work, we derive the optimal oscillator-to-oscillator codes among the general family of Gottesman-Kitaev-Preskill (GKP)-stablizer codes for homogeneous noise. We prove that an arbitrary GKP-stabilizer code can be reduced to a generalized GKP two-mode-squeezing (TMS) code. The optimal encoding to minimize the geometric mean error can be constructed from GKP-TMS codes with an optimized GKP lattice and TMS gains. For single-mode data and ancilla, this optimal code design problem can be efficiently solved, and we further provide numerical evidence that a hexagonal GKP lattice is optimal and strictly better than the previously adopted square lattice. For the multimode case, general GKP lattice optimization is challenging. In the two-mode data and ancilla case, we identify the D4 lattice—a 4-dimensional dense-packing lattice—to be superior to a product of lower dimensional lattices. As a by-product, the code reduction allows us to prove a universal no-threshold-theorem for arbitrary oscillators-to-oscillators codes based on Gaussian encoding, even when the ancilla are not GKP states
Entanglement from superradiance and rotating quantum fluids of light
The amplification of radiation by superradiance is a universal phenomenon
observed in numerous physical systems. We demonstrate that superradiant
scattering generates entanglement for different input states, including
coherent states, thereby revealing the inherently quantum nature of this
phenomenon. To put these concepts to the test, we propose a novel approach to
create horizonless ergoregions, which are nonetheless dynamically stable thanks
to the dissipative dynamics of a polaritonic fluid of light. We numerically
simulate the system to demonstrate the creation of a stable ergoregion, and
experimentally realize a comparable configuration. Subsequently, we investigate
rotational superradiance within this system, with a primary focus on
entanglement generation and the possibilities for its enhancement using current
techniques. Our methods permit the investigation of quantum emission by
rotational superradiance by controlling the input state at will.Comment: 13 pages with 10 figures + 9 pages (references + appendices with an
extra figure and a table with numerical data
Global Time Distribution via Satellite-Based Sources of Entangled Photons
We propose a satellite-based scheme to perform clock synchronization between
ground stations spread across the globe using quantum resources. We refer to
this as a quantum clock synchronization (QCS) network. Through detailed
numerical simulations, we assess the feasibility and capabilities of a
near-term implementation of this scheme. We consider a small constellation of
nanosatellites equipped only with modest resources. These include quantum
devices such as spontaneous parametric down conversion (SPDC) sources,
avalanche photo-detectors (APDs), and moderately stable on-board clocks such as
chip scale atomic clocks (CSACs). In our simulations, the various performance
parameters describing the hardware have been chosen such that they are either
already commercially available, or require only moderate advances. We conclude
that with such a scheme establishing a global network of ground based clocks
synchronized to sub-nanosecond level (up to a few picoseconds) of precision,
would be feasible. Such QCS satellite constellations would form the
infrastructure for a future quantum network, able to serve as a globally
accessible entanglement resource. At the same time, our clock synchronization
protocol, provides the sub-nanosecond level synchronization required for many
quantum networking protocols, and thus, can be seen as adding an extra layer of
utility to quantum technologies in the space domain designed for other
purposes.Comment: 20 pages, 12 figures and 6 tables. Comments are welcom
Systematic analysis of Plasmodium myosins reveals differential expression, localisation, and function in invasive and proliferative parasite stages
The myosin superfamily comprises of actin‐dependent eukaryotic molecular motors important in a variety of cellular functions. Although well studied in many systems, knowledge of their functions in Plasmodium, the causative agent of malaria, is restricted. Previously, six myosins were identified in this genus, including three Class XIV myosins found only in Apicomplexa and some Ciliates. The well characterized MyoA is a Class XIV myosin essential for gliding motility and invasion. Here, we characterize all other Plasmodium myosins throughout the parasite life cycle and show that they have very diverse patterns of expression and cellular location. MyoB and MyoE, the other two Class XIV myosins, are expressed in all invasive stages, with apical and basal locations, respectively. Gene deletion revealed that MyoE is involved in sporozoite traversal, MyoF and MyoK are likely essential in the asexual blood stages, and MyoJ and MyoB are not essential. Both MyoB and its essential light chain (MCL‐B) are localised at the apical end of ookinetes but expressed at completely different time points. This work provides a better understanding of the role of actomyosin motors in Apicomplexan parasites, particularly in the motile and invasive stages of Plasmodium during sexual and asexual development within the mosquito
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