Quantum Physics Research
Bragg Atom Interferometer Sets New Upper Bound on CSL Collapse Rate with 99% Fringe Contrast
A high-contrast Bragg atom interferometer achieving 99% fringe visibility at interrogation times up to 60 ms has been used to constrain the Continuous Spontaneous Localization (CSL) model — a leading candidate for explaining wavefunction collapse. By systematically identifying and correcting contras…
Power-Law Deformations of Gaussian States Reveal Three Distinct Topological Regimes Without Sharp Phase Transitions
Starting from the Kitaev Majorana chain ground state, this work applies imaginary-time evolution with power-law coupled quadratic Hamiltonians (~1/r^α) to probe how long-range interactions affect topological phase access. Because the deformed states remain Gaussian, entanglement and correlation func…
Periodic Orbit Theory Explains Random Matrix Universality in Chaotic Many-Body Quantum Circuits
Kieler, Fritzsch, and Bäcker extend periodic orbit theory — the established semiclassical bridge between single-particle quantum chaos and random matrix theory (RMT) — to deterministic many-body systems with explicit subsystem structure. They identify a new class of periodic orbit families unique to…
Quantum Fluctuations Can Regularize Chaos in Many-Body Spin Systems: A 2PI Framework Demonstration
This paper investigates beyond-mean-field dynamics in a fully connected SU(3) spin-exchange model, using the two-particle irreducible (2PI) effective action formalism to capture higher-order quantum correlations. The central finding is that quantum fluctuations can regularize — effectively suppress …
Quantum Devices Are Outpacing Theory for Time Crystals — A New Classification Framework Is Needed
Time crystals — nonequilibrium phases of matter exhibiting spontaneous temporal ordering in driven many-body quantum systems — have advanced beyond the reach of existing theoretical paradigms, as demonstrated by recent experiments on quantum processors. Camacho and Fauseweh review quantum hardware i…
Tensor Networks Crack the Hard Problem of Quantum Electromechanical Self-Oscillations
Self-sustained mechanical oscillations driven by static electrochemical bias in nanoscale electromechanical systems have been analytically intractable due to the simultaneous presence of large bosonic Hilbert spaces, strong interactions, and structured fermionic leads. This paper introduces a tensor…
Twisted Light as a Unified Photonic Control Layer for Quantum Dot Qubits
Rodriguez et al. demonstrate that orbital angular momentum (OAM)-carrying "twisted light" can access many-body correlation sectors in few-electron quantum dots that are invisible to conventional dipolar probes, enabling a unified WRITE/READ/SCALE control primitive for quantum computing. The selectio…
Quantum Coherence Decomposes Into Heat and Work: No New Thermodynamic Category Needed
This paper presents a time-dependent perturbative framework for the quantum first law, expanding thermodynamic quantities to second order to derive explicit corrections for work, heat, and coherence. The central result is that quantum coherence contributions — previously treated as an independent en…
PEPSKit.jl: A Julia-Native iPEPS Simulation Framework with Full Symmetry and Fermion Support
PEPSKit.jl is a new Julia package for simulating two-dimensional quantum many-body systems using infinite projected entangled-pair states (iPEPS), built atop the TensorKit.jl tensor computation backend. It provides high-level algorithms covering ground-state, time-evolution, and finite-temperature r…
A Contextual Phase Mechanism Proposed to Explain Wavefunction Collapse in Entangled Subsystem Measurements
Scholes (arXiv:2605.20111) proposes a concrete mechanism for wavefunction collapse in entangled quantum systems, centered on a "contextual phase" that is randomly installed into an entangled state at its formation. This phase locks the entangled subsystems together and deterministically directs the …
The Cosine Problem in Quantum Gravity is a Feature, Not a Bug: Path Integrals Resolve the Problem of Time
Diaz and Perez use the path integral formulation to show that time evolution is an emergent phenomenon in timeless closed quantum systems — a tractable model for generally covariant theories like quantum gravity. Their key result is that the so-called "cosine problem" (transition amplitudes of the f…
Engineering g-Tensor Anisotropy in Ge/SiGe Quantum Dots to Enable Reliable Hole-Spin Qubit Operation
Planar germanium heterostructures are a leading candidate for scalable semiconductor quantum computing, but qubit performance is degraded by quantum dot variability that causes uncertain energy levels and random spin quantization axis orientations. This paper introduces a numerical optimization fram…
Postselection Slows Entanglement Decay in Transmon Qubits via PT-Symmetry Breaking at Exceptional Points
This paper investigates entanglement dynamics in a transmon-cavity-transmon system under continuous measurement and postselection, operating in the dispersive regime where an effective qubit-qubit coupling arises via virtual cavity excitations. The authors demonstrate that postselection — retaining …
Classical Spin Simulations Diverge from Quantum Solutions in Dipolar Systems Across All Timescales
This paper directly challenges the common use of classical spin simulations as proxies for quantum spin dynamics in dipole-coupled systems. By solving the Schrödinger equation exactly and comparing against classical spin simulations using Free Induction Decay (FID) as a benchmark, the authors show t…
Optical Depth as the Universal Scaling Parameter for Cooperative Emission in Atomic Ensembles
This paper derives a universal scaling law for many-body cooperative (superradiant) emission in free-space atomic ensembles, unifying ordered arrays and disordered clouds across arbitrary dimensions. The maximum photon emission rate scales as the product of atom number and optical depth, with optica…
Cavity QED as a Contextual Stern-Gerlach Analogue: Measurement-Driven Dressed-State Polarization
Mavrogordatos proposes a cavity/circuit QED analogue of the Stern-Gerlach experiment in which a two-level atomic transition's pseudo-spin replaces physical spin and a resonant driving field replaces the magnetic field. Phase-sensitive continuous homodyne-style detection of the cavity field destabili…
Superconducting Processors Achieve Simultaneous High-Dimensional and Many-Body Bell Non-Locality at d=64
Mafi et al. demonstrate Bell inequality violations in a regime previously inaccessible to experiment: simultaneously high-dimensional (d=64) and many-body, using 12 qubits on a superconducting quantum processor. For system sizes up to d=32, the observed nonlocal correlations exceed the quantum upper…
Witness-Based Framework for CV to DV Entanglement and EPR Steering Activation
This paper introduces a novel witness-based framework for quantifying and activating continuous-variable (CV) resources into discrete-variable (DV) bipartite entanglement or Einstein-Podolsky-Rosen (EPR) steering. It defines infinite families of bounded-witness monotones for three standard CV resour…
Time-Dependent Logarithmic Perturbation Theory for Quantum Systems
This paper introduces a time-dependent extension of logarithmic perturbation theory for nonrelativistic quantum dynamics. It preserves the closed-integral structure of corrections, enabling the computation of instantaneous and dynamic energy shifts. The method provides a promising analytical approac…
Unconventional Photon Blockade Via Symmetrically Driven Nonlinear Dimer
This paper details a robust method for achieving unconventional photon blockade (UPB) in a symmetric Kerr dimer. The proposed scheme, driven by equal-amplitude fields with a 90-degree phase difference, offers strong antibunching and is resilient to fabrication disorder through retuning the drive pha…
Pulsed Fiber Amplifiers Achieve CW-Equivalent Coherence for Scalable Rydberg Atom Arrays
A fiber-based master-oscillator power-amplifier (MOPA) system has been demonstrated to enable efficient coherent Rydberg excitation of single rubidium atoms, matching the performance of continuous-wave (CW) laser methods. The key engineering challenge — that pulsed amplifiers suffer from pulse disto…
Attosecond Streaking Enables Sub-Cycle Quantum-Optical Metrology of Intense Light Fields
This paper proposes attosecond streaking as a practical route to characterizing the quantum state of intense light fields at sub-cycle timescales — a regime inaccessible to existing methods. Using a Feynman–Vernon framework, the authors decompose photoelectron dynamics into coherent and fluctuation …
Unified Response Theory for Isolated Quantum Fields: Causality, Fluctuation-Dissipation, and Functional Methods
This 56-page review by Stefan Floerchinger (arXiv:2604.13637) systematically develops response theory for isolated quantum field systems undergoing unitary time evolution — a regime distinct from open systems coupled to thermal baths. The paper emphasizes the spectral consequences of causality for l…
Sequential STIRAP and Microwave-Dressing Staging Pushes Trapped Rydberg Ion Gate Fidelity to 99.93%
Simultaneous STIRAP excitation and microwave-induced dipole-dipole interaction in trapped Rydberg ion gates causes dark-state distortion and intermediate-state decay, degrading gate fidelity. Zlatanov et al. propose a decoupled pulse ordering — executing STIRAP and microwave dressing in separate seq…
Multi-Detector Arrays Linearly Scale Entanglement Harvesting from Quantum Vacuum
This paper investigates bipartite entanglement harvesting from a massless scalar field's quantum vacuum using multi-detector Unruh-DeWitt systems. Using perturbation theory, the authors show that leading-order negativity is governed by a linearly-scaling submatrix of the reduced density matrix, maki…
Skyrmions Realized in 150+ Ion Penning Trap Crystal with Near-Unity Winding Number
Researchers have experimentally realized topological spin textures — specifically skyrmions — in a two-dimensional crystal of over 150 trapped ions in a Penning trap, a scale and programmability previously unachieved for such structures. Using globally applied spin-dependent forces, they determinist…
Secular Approximation Breakdown Enables Transient Entanglement Enhancement in Driven Chiral Quantum Networks
This paper investigates transient entanglement generation between two quantum nodes coupled via a chiral 1D channel, demonstrating that continuous driving can push maximum concurrence above the canonical 2/e limit associated with single-excitation models. The enhancement mechanism is traced to the f…
Fabry-Pérot Interference as a Diagnostic and Design Tool for High-Gain Josephson Parametric Amplifiers
This paper presents a flux-driven, lumped-element Josephson parametric amplifier (JPA) based on a SQUID array, achieving near-quantum-limited performance with up to 44 dB gain and ~50 MHz bandwidth at 20 dB. A key contribution is the identification that high-gain broadband JPAs are highly sensitive …
Quantifying Symmetry Drift Under Perturbation: The Wandering Range Framework for Robust Quantum Symmetries
This paper introduces the "wandering range" as a formal measure of how much a robust symmetry S of a Hamiltonian H deviates under perturbed time evolution e^{it(H+εV)} relative to the unperturbed case where S is exactly preserved. The key contribution is identifying conditions under which the wander…
Momentum-Space Entanglement Entropy as a Diagnostic for Dynamical Quantum Phase Transitions
This paper demonstrates that momentum-space entanglement entropy, when measured in the post-quench eigenbasis, serves as a time-independent and robust diagnostic for dynamical quantum phase transitions (DQPTs) in translationally invariant two-band systems. The study establishes a geometric link betw…
Zero-Photon Ghost Imaging Explained by Photon-Number Projection and Thermal Light Statistics
This paper presents a novel ghost imaging technique where images are reconstructed without any photons interacting with the object, or even without photons in either the signal or reference beams. This "zero-photon" ghost imaging relies on discarding all photons that interact with the object and exc…
Mathematical Obstructions to Dirac Path Measures
This paper revisits the long-standing problem of why a well-defined probability measure for a classical path integral representation of the Dirac equation in Minkowski space does not exist. It unifies two previously separate viewpoints: Zastawniak's observation regarding the distributional character…
Environmental Decoherence Improves Semi-Classical Quantum Approximations
This paper demonstrates that incorporating environmental decoherence into semi-classical models significantly improves their accuracy, achieving exact descriptions of original quantum dynamics within a toy model. This approach rectifies the limitations of standard mean-field semi-classical methods b…
Exact One-to-One Mapping Unites HEOM and Pseudomode Methods for Non-Markovian Quantum Dynamics
The paper establishes a precise equivalence between the Hierarchical Equations of Motion (HEOM) and pseudomode methods for open quantum systems with bath correlation functions (BCFs) as sums of N exponentials. Every such BCF corresponds to a physical model of N interacting pseudomodes damped via Lin…
Disorder-Induced Superfluidity Observed in Qutrit System
This research experimentally demonstrates disorder-induced superfluidity on a superconducting processor utilizing qutrit readout and control. The study identifies regions of non-vanishing condensate fraction through spatially-resolved two-point correlator measurements and observes a linearly-dispers…