Absence of barren plateaus in finite local-depth circuits with long-range entanglement DOI Creative Commons
Hao-Kai Zhang, Shuo Liu, Shi‐Xin Zhang

et al.

arXiv (Cornell University), Journal Year: 2023, Volume and Issue: unknown

Published: Jan. 1, 2023

Ground state preparation is classically intractable for general Hamiltonians. On quantum devices, shallow parameterized circuits can be effectively trained to obtain short-range entangled states under the paradigm of variational eigensolver, while deep are generally untrainable due barren plateau phenomenon. In this Letter, we give a lower bound on variance circuit gradients arbitrary composed local 2-designs. Based our unified framework, prove absence plateaus in training finite local-depth (FLDC) ground FLDCs allowed conventional depth generate long-range states, such as topologically ordered but their depths finite, i.e., there only number gates acting individual qubits. This characteristic sets FLDC apart from circuits: cannot simulated estimate observables efficiently by existing tensor network methods two and higher dimensions. We validate analytical results with extensive numerical simulations demonstrate effectiveness using generalized toric code model.

Language: Английский

Light–matter interactions in quantum nanophotonic devices DOI
Alejandro González-Tudela, Andreas Reiserer, Juan José García‐Ripoll

et al.

Nature Reviews Physics, Journal Year: 2024, Volume and Issue: 6(3), P. 166 - 179

Published: Jan. 25, 2024

Language: Английский

Citations

37
Remote Charging and Degradation Suppression for the Quantum Battery DOI
Wan-Lu Song, Haibin Liu, Bin Zhou

et al.

Physical Review Letters, Journal Year: 2024, Volume and Issue: 132(9)

Published: Feb. 27, 2024

The quantum battery (QB) makes use of effects to store and supply energy, which may outperform its classical counterpart. However, there are two challenges in this field. One is that the environment-induced decoherence causes energy loss aging QB, other decreasing charger-QB coupling strength with increasing their distance charging QB become inefficient. Here, we propose a scheme realize remote via charger rectangular hollow metal waveguide. It found an ideal realized as long bound states formed spectrum total system consisting charger, electromagnetic environment Using constructive role decoherence, our immune aging. Additionally, without resorting direct interaction, works way long-range wireless-like charging. Effectively overcoming challenges, result supplies insightful guideline practical realization by reservoir engineering.

Language: Английский

Citations

26
Absence of Barren Plateaus in Finite Local-Depth Circuits with Long-Range Entanglement DOI
Hao-Kai Zhang, Shuo Liu, Shi‐Xin Zhang

et al.

Physical Review Letters, Journal Year: 2024, Volume and Issue: 132(15)

Published: April 9, 2024

Ground state preparation is classically intractable for general Hamiltonians. On quantum devices, shallow parametrized circuits can be effectively trained to obtain short-range entangled states under the paradigm of variational eigensolver, while deep are generally untrainable due barren plateau phenomenon. In this Letter, we give a lower bound on variance circuit gradients arbitrary composed local 2-designs. Based our unified framework, prove absence plateaus in training finite local-depth (FLDC) ground FLDCs allowed conventional depth generate long-range states, such as topologically ordered but their depths finite, i.e., there only number gates acting individual qubits. This characteristic sets FLDC apart from circuits: cannot simulated estimate observables efficiently by existing tensor network methods two and higher dimensions. We validate analytical results with extensive numerical simulations demonstrate effectiveness using generalized toric code model.

Language: Английский

Citations

11
Dipole-dipole interactions mediated by a photonic flat band DOI Creative Commons
Enrico Di Benedetto, Alejandro González-Tudela, Francesco Ciccarello

et al.

Quantum, Journal Year: 2025, Volume and Issue: 9, P. 1671 - 1671

Published: March 25, 2025

Flat bands (FBs) are energy with zero group velocity, which in electronic systems were shown to favor strongly correlated phenomena. Indeed, a FB can be spanned basis of strictly localized states, the so called compact states (CLSs), yet generally non-orthogonal. Here, we study emergent dipole-dipole interactions between emitters dispersively coupled photonic analogue FB, setup within reach state-of the-art experimental platforms. We show that strength such photon-mediated decays exponentially distance characteristic localization length which, unlike typical behaviours standard bands, saturates finite value as emitter's approaches FB. Remarkably, find grows overlap CLSs according an analytically-derived universal scaling law valid for large class FBs both 1D and 2D. Using giant atoms (non-local atom-field coupling) allows tailor interaction potentials having same shape CLS or superposition few these.

Language: Английский

Citations

1
Dynamical Excitation Control and Multimode Emission of an Atom-Photon Bound State DOI Creative Commons
Claudia Castillo-Moreno, Kazi Rafsanjani Amin, Ingrid Strandberg

et al.

Physical Review Letters, Journal Year: 2025, Volume and Issue: 134(13)

Published: March 31, 2025

Atom-photon bound states arise from the coupling of quantum emitters to band edge dispersion-engineered waveguides. Thanks their tunable-range interactions, they are promising building blocks for simulators. Here, we study dynamics an atom-photon state emerging a frequency-tunable emitter—a transmon-type superconducting circuit—to microwave metamaterial. Employing precise temporal control over frequency detuning emitter edge, examine transition adiabatic nonadiabatic behavior in formation and its melting into propagating modes Moreover, experimentally observe multimode emission state, triggered by fast change emitter’s frequency. Our Letter offers insight dynamic preparation APBS provides method characterize photonic content, with implications optics simulation. Published American Physical Society 2025

Language: Английский

Citations

1
Trainability enhancement of parameterized quantum circuits via reduced-domain parameter initialization DOI
Yabo Wang, Bo Qi, Christopher Ferrie

et al.

Physical Review Applied, Journal Year: 2024, Volume and Issue: 22(5)

Published: Nov. 4, 2024

Parameterized quantum circuits (PQCs) have been widely used as a machine learning model to explore the potential of achieving advantages for various tasks.However, training PQCs is notoriously challenging owing phenomenon plateaus and/or existence (exponentially) many spurious local minima.To enhance trainability, in this work we propose an efficient parameter initialization strategy with theoretical guarantees.We prove that by reducing initial domain each inversely proportional square root circuit depth, magnitude cost gradient decays at most polynomially respect qubit count and depth.Our results are substantiated through numerical simulations variational eigensolver tasks.Moreover, demonstrate reduced-domain can protect specific neural networks from exponentially minima.Our highlight significance appropriate strategy, offering insights trainability convergence algorithms.

Language: Английский

Citations

8
Quantum computing with subwavelength atomic arrays DOI
Freya Shah, Taylor L. Patti, Oriol Rubies-Bigordà

et al.

Physical review. A/Physical review, A, Journal Year: 2024, Volume and Issue: 109(1)

Published: Jan. 16, 2024

Photon-mediated interactions in subwavelength atomic arrays have numerous applications quantum science. In this paper, we explore the potential of three-level emitters, or ``impurities'' embedded a two-dimensional array to serve as platform for computation. By exploiting altered behavior impurities result induced dipole-dipole mediated by arrays, design and simulate set universal gates consisting $\sqrt{\text{i}\mathrm{SWAP}}$ single-qubit rotations. We demonstrate that these very high fidelities due long coherence times, atoms remain within proximal range. Finally, circuits leading generation maximally entangled two-qubit Bell states, well three-qubit Greenberger-Horne-Zeilinger state. These findings establish emitter an alternative computation simulation.

Language: Английский

Citations

4
Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics DOI Creative Commons
Aviv Karnieli, Offek Tziperman, Charles Roques‐Carmes

et al.

Physical Review Research, Journal Year: 2025, Volume and Issue: 7(1)

Published: Jan. 21, 2025

Enhancing interactions in many-body quantum systems, while protecting them from environmental decoherence, is at the heart of many technologies. Waveguide electrodynamics a promising platform for achieving this, as it hosts infinite-range and decoherence-free subspaces emitters. However, coherent between emitters are typically washed out wavelength-spacing regime hosting states, control over latter becomes limited, Hamiltonians this important remain reach. Here we show that by incorporating emitter arrays with nonlinear waveguides parametric gain, obtain unique class interaction coupling strengths increase spacing, persist even wavelength-spaced arrays. We then propose to use these coherently generate states directly ground state, using only global squeezing drives, without need local addressing individual Interestingly, find dynamics approaches unitary evolution limit weak intrawaveguide squeezing, discuss potential experimental realizations effect. Our results pave way towards protocols waveguide electrodynamics, applications including computing, simulation, memory, nonclassical light generation. Published American Physical Society 2025

Language: Английский

Citations

0
Waveguide QED with dissipative light-matter couplings DOI Creative Commons

Xing‐Liang Dong,

Fuli Li, Zongping Gong

et al.

Physical Review Research, Journal Year: 2025, Volume and Issue: 7(1)

Published: Feb. 19, 2025

Dissipative light-matter coupling plays a vital role in non-Hermitian physics, but it remains largely unexplored waveguide QED systems. In this work, we find that by employing pseudo-Hermitian symmetry rather than anti-PT symmetry, the concept of dissipative could be generalized and applied to field QED. This leads series intriguing results, such as spontaneous breaking across exceptional points (EPs), level attraction between bound states, critical transition EPs for population quantum emitters state. Thanks tunability photonic bands crystal waveguides, also demonstrate emergence nonstandard third-order with chiral spatial profiles topological system. work provides promising paradigm studying phenomena Published American Physical Society 2025

Language: Английский

Citations

0
Long-Range Interactions in Weyl-Dense Atomic Arrays Protected from Dissipation and Disorder DOI
Iñaki García-Elcano, Paloma A. Huidobro, Jorge Bravo‐Abad

et al.

Physical Review Letters, Journal Year: 2025, Volume and Issue: 134(12)

Published: March 28, 2025

Long-range interactions are a key resource in many quantum phenomena and technologies. Free-space photons mediate power-law but lack tunability suffer from decoherence processes due to their omnidirectional emission. Engineered dielectrics can yield tunable coherent interactions, typically at the expense of making them both shorter ranged sensitive material disorder photon loss. Here, we propose platform that circumvent all these limitations based on three-dimensional subwavelength atomic arrays subjected magnetic fields. Our result is show how design polaritonic bands metamaterials feature pair frequency-isolated Weyl points, i.e., points reciprocal space around which disperse linearly defining monopoles Berry curvature. As predicted by recent works, such excitations simultaneously long range, gapless nature; robust, topological protection points; decoherence-free, subradiant character. We demonstrate robustness isolated for large regime interatomic distances field values characterize emergence corresponding Fermi arcs surface states. The latter lead two-dimensional, nonreciprocal with no analogue other chiral optical setups.

Language: Английский

Citations

0