Quantum Physics · Cross-listed from physics.ins-det
Detuning-insensitive wide-field imaging of vector microwave fields with diamond sensors
Xiu-Qi Chen, Rui-Zhi Zhang, Gang-Qin Liu et al. (+1 more)
Nitrogen vacancy (NV) centers in diamond have precipitated profound advances in microwave detection, manifesting themselves both in spatial resolution and sensitivity. However, typical methods based on Rabi oscillations are subject to detunings due to thermal and
magnetic fluctuations and/or gradients, which introduce systematic errors and render the measurements susceptible to environmental perturbations. Here, we propose and demonstrate a novel approach for determining both the magnitude and direction of microwaves, by exploiting the spectral line broadening effect in the optically detected
magnetic resonance of NV centers. This method eliminates the requirement of aligning the MW frequency to the
spin transitions and is therefore immune to variations and inhomogeneities of the
magnetic field and temperature, providing an optimal tool for fast imaging applications. With this method, we achieved wide-field imaging of near field microwaves generated with a microscale $\rm{\Omega}$-pattern
antenna with a resolution of 800\,nm. Combining with the vector detection using multi-axis NVs, a full reconstruction of the vector microwave fields is obtained. Besides, our scheme also exhibits excellent linearity over a broad range of MW amplitudes, and the scale is theoretically calculated to be more than four orders. Our results augment the applicability of diamond-based microwave devices in applications under complex scenarios, especially where large dynamic range, fast test speed, and high spatial resolution are demanded.
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All authors Xiu-Qi Chen, Rui-Zhi Zhang, Gang-Qin Liu, Huijie Zheng
Quantum Physics
On the Dynamics of Multiparticle Carroll-Schrd̈inger Quantum Systems
José Rojas and Melvin Arias
We study the dynamics of multiparticle Carroll-Schrödinger (CS)
quantum systems in $1{+}1$ dimensions, where $x$ acts as the
evolution variable and $t$ as the configuration coordinate. We derive the $N$-body theory on equal-$x$ slices as the Carrollian limit of a relativistic multi-time Klein-Gordon model, introducing temporal interactions via minimal coupling to the temporal energy operators. An $x$-dependent gauge transformation maps this to an equivalent description with explicit many-body potentials, illustrated by a temporal coupled-oscillator model that exhibits synchronization. Adopting a complementary spatial viewpoint with a static potential $U_{\!tot}(\mathbf x)$, we show that the
evolution is driven by the collective force $\sum_j\partial_{x_j}U_{\!tot}$; for any translation-invariant interaction (such as a regularized Coulomb potential), these internal forces cancel, rendering the collective dynamics free and highlighting Carrollian ultralocality. We also construct a coordinate duality mapping separable Schrödinger
Hamiltonians to CS generators via Schwarzian derivatives. Exchange
symmetry is formulated in the time domain, yielding temporal bunching for
bosons and antibunching for
fermions via the second-order coherence function $g^{(2)}(t,t')$. In second quantization, the contact limit yields a temporal derivative cubic–quintic nonlinear Schrödinger equation with a theoretically fixed nonlinearity coefficient $\beta=-3/16$. Finally, by coupling canonical pairs to external scalar and gauge fields, we establish an isomorphism with one-dimensional current-density functional theory, outlining a Carrollian Hohenberg-Kohn mapping and Kohn-Sham scheme.
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Quantum Physics · Cross-listed from hep-ph
Searching for Ultralight Dark Matter with MOLeQuTE: a Massive Optically Levitated Quantum Tabletop Experiment
Louis Hamaide, Hannah Banks, Peter Barker et al. (+1 more)
Many well theoretically motivated models of ultralight dark matter are expected to give rise to feeble oscillatory forces on macroscopic objects. Optically trapped sensors have high force sensitivities but have remained relatively unexplored in this context. In this work we propose a new, tunable, optically trapped sensor specifically designed to detect such forces. Our design features a high-mass ($\sim$ mg) plate whose high aspect ratio allows its weight to be supported by a vertical beam without excessive heating. We present the first systematic analysis and optimisation of
quantum noises in optically trapped systems and show that our setup has the potential to operate at the standard
quantum limit with current off-the-shelf technologies. We demonstrate that our sensor could offer unique access to large regions of uncharted parameter space of vector B-L dark matter, with projected sensitivities that could advance existing limits by several orders of magnitude over a broad range of frequencies.
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All authors Louis Hamaide, Hannah Banks, Peter Barker, Andrew A. Geraci
Quantum Physics · Cross-listed from hep-lat
When the center matters: color screening and gluelumps in dihedral lattice gauge theories
Pavel P. Popov, Edoardo Ballini, Alberto Bottarelli et al. (+4 more)
Confinement is one of the hallmarks of
quantum chromodynamics (QCD), but its first-principles characterization remains elusive. We show that discrete non-Abelian
lattice gauge theories (LGTs) with dihedral groups $D_N$ provide a minimal setup for characterizing the connection between confinement and the group center. When the latter is trivial (odd $N$),
gluon clouds screen static charges, forming composite objects known as gluelumps. These are stable excitations of the theory, in contrast to their QCD analog. As a consequence, string breaking can occur through fluctuations of the electric field only, without pair nucleation from the
vacuum. Our results showcase how the rich physics typically associated with QCD emerges in much simpler discrete non-Abelian LGTs, making them ideal settings to test this phenomenology both in numerical calculations and in near-term
quantum devices.
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All authors Pavel P. Popov, Edoardo Ballini, Alberto Bottarelli, Michele Burrello, Pietro Silvi, Matteo M. Wauters, Philipp Hauke
Quantum Physics
Tailoring Bell inequalities to the qudit toric code and self testing
Eloïc Vallée, Owidiusz Makuta, Patrick Emonts et al. (+2 more)
Bell nonlocality provides a robust scalable route to the efficient certification of
quantum states. Here, we introduce a general framework for constructing Bell inequalities tailored to the $\mathbb{Z}_d$ toric code for odd
prime local dimensions. Selecting a suitable subset of stabilizer operators and mapping them to generalized measurement observables, we compute multipartite Bell expressions whose
quantum maxima admit a sum-of-squares decomposition. We show that these inequalities are maximally violated by all states in the ground-state
manifold of the $\mathbb{Z}_d$ toric code, and determine their classical (local) bounds through a combination of combinatorial tiling arguments and explicit optimization. As a concrete application, we analyze the case of $d=3$ and demonstrate that the maximal violation self-tests the full qutrit toric-code subspace, up to local isometries and complex conjugation. This constitutes, to our knowledge, the first-ever example of self-testing a qutrit subspace. Extending these constructions, we further present schemes to enhance the ratio of classical–
quantum bounds and thus improve robustness to experimental imperfections. Our results establish a pathway toward device-independent certification of highly entangled topological
quantum matter and provide new tools for validating qudit states in error-correcting codes and
quantum simulation platforms.
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All authors Eloïc Vallée, Owidiusz Makuta, Patrick Emonts, Rhine Samajdar, Jordi Tura
Quantum Physics · Cross-listed from physics.ed-ph
High schoolers excel at Oxford quantum course using pictorial mathematics
Bob Coecke, Aleks Kissinger, Stefano Gogioso et al. (+12 more)
We are at the dawn of the second
quantum revolution, where our ability to create and control individual
quantum systems is poised to drive transformative advancements in basic science, computation, and everyday life. However,
quantum theory has long been conceived as notoriously hard to learn, creating a significant barrier to workforce development, informed decision-making by stakeholders and policymakers, and broader public understanding. This paper is concerned with
Quantum Picturalism, a novel visual mathematical
language for
quantum physics. Originally developed over two decades ago to explore the foundational structure of
quantum theory, this rigorous diagrammatic framework has since been adopted in both academia and industry as a powerful tool for
quantum computing research and software development. Here, we demonstrate its potential as a transformative educational methodology. We report the findings from a pilot study involving 54 UK high school students, randomly selected from a pool of 734 volunteers across the UK. Despite the absence of advanced mathematical prerequisites, these students demonstrated a strong conceptual grasp of key
quantum principles and operations. On an assessment comprising university graduate-level exam questions, participants achieved an 82% pass rate, with 48% obtaining a distinction-level grade. These results pave the way for making
quantum more inclusive, lowering traditional cognitive and demographic barriers to
quantum learning. This approach has the potential to broaden participation in the field and provide a promising new entry point for stakeholders, future experts, and the general public.
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All authors Bob Coecke, Aleks Kissinger, Stefano Gogioso, Selma Dündar-Coecke, Caterina Puca, Lia Yeh, Muhammad Hamza Waseem, Emmanuel M. Pothos, Sieglinde Pfaendler, Vincent Wang-Mascianica, Thomas Cervoni, Ferdi Tomassini, Vincent Anandraj, Peter Sigrist, Ilyas Khan
Quantum Physics · Cross-listed from q-bio.NC
An Operational Quantum Information Framework for Experimental Studies on Color Perception
Roberto Leporini, Edoardo Provenzi and Michel Berthier
Starting from the foundational axiomatization of the perceptual color space initiated by Schrödinger in 1920 and eventually refined by Resnikoff in 1974, Berthier, Provenzi and their collaborators have recently proposed a reformulation of perceptual color attributes within the framework of
quantum information. Their work is based on the Jordan
algebra formalism of
quantum theories and, more specifically, on a
quantum system described by a
spin factor over the field of real numbers. This theoretical framework is not that of ordinary
quantum mechanics, mainly because it requires dealing with rebits, whereas the latter uses
qubits. The aim of this paper is to show that this difference in no way hinders the implementation of experimental protocols for testing the validity of the predictions of the color perception model. In particular, we show how to compute the
quantum information based perceptual attributes of perceived colors in terms of
qubit density
matrices.
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Quantum Physics · Cross-listed from cs.PL
RapunSL: Untangling Quantum Computing with Separation, Linear Combination and Mixing
Yusuke Matsushita, Kengo Hirata, Ryo Wakizaka et al. (+1 more)
Quantum Separation Logic (QSL) has been proposed as an effective tool to improve the scalability of deductive
reasoning for
quantum programs. In QSL, separation is interpreted as disentanglement, and the frame rule brings a notion of
entanglement-local specification (one that only talks about the
qubits entangled with those acted upon by the program). In this paper, we identify two notions of locality unique to the
quantum domain, and we construct a novel
quantum separation logic, RapunSL, which is able to soundly reduce
reasoning about superposition states to
reasoning about pure states (basis-locality), and
reasoning about mixed states arising from measurement to
reasoning about pure states (outcome-locality). To do so, we introduce two connectives, linear combination and mixing, which together with separation provide a dramatic improvement in the scalability of
reasoning, as we demonstrate on a series of challenging case studies.
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All authors Yusuke Matsushita, Kengo Hirata, Ryo Wakizaka, Emanuele D'Osualdo
Quantum Physics
Spectral analysis of the Koopman operator as a framework for recovering Hamiltonian parameters in open quantum systems
Jorge E. Pérez-García, Carlos Colchero and Julio C. Gutiérrez-Vega
Accurate identification of
Hamiltonian parameters is essential for modeling and controlling open
quantum systems. In this work, we demonstrate that the multichannel Hankel alternative view of Koopman (mHAVOK)
algorithm is a robust and reliable spectral data-driven method for retrieving
Hamiltonian parameters from the
evolution of first-moment observables in open
quantum systems. The method relies on the discrete spectrum of the Koopman operator to obtain these parameters, which are computed using the mHAVOK
algorithm; a theoretical connection to this affirmation is presented. The method is tested on noiseless quadratures of an open two-dimensional
quantum harmonic oscillator and shown to retrieve oscillation frequencies, damping rates, nonlinear Kerr shifts, the
qubit-
photon coupling strength of a Jaynes-Cummings interaction, and the modulated frequency of a time-dependent
Hamiltonian. The majority of the recovered parameters remained within 5% of their actual values. Compared with
Fourier and
matrix-pencil
estimators, our approach yields lower errors for dynamics with strong dissipation. Overall, these findings suggest that Koopman operator theory provides a practical framework for studying
quantum dynamical systems.
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Quantum Physics · Cross-listed from physics.atom-ph
Arbitrary control of the temporal waveform of photons during spontaneous emission
Carl Thomas, Rebecca Munk and Boris Blinov
Control of the temporal waveform of
photons produced during spontaneous emission from single
quantum emitters provides a crucial tool in the establishment of hybrid
quantum systems, optimization of
quantum state transfer protocols and mitigation of effects due interferometric instability for network architectures based on flying
qubits. We describe a method to generate
photons of any temporal waveform from emitters of any excited state lifetime, limited only by the timing resolution of control hardware. We show how the temporal waveform of
photons can be controlled by deterministically varying the population of an excited state which undergoes spontaneous emission. Our broadly applicable approach has only two requirements for a candidate
quantum emitter: modulation of the (1) amplitude and (2) relative phase of a field coupling a ground state to the excited
manifold. We detail how to identify optimal excitation pulses by employing variational
algorithms to feed back on atomic populations. Additionally, we develop
Quantum Monte Carlo based tools to determine
photon-number statistics and establish techniques to identify optimal excitation strengths and post-selection thresholds for
photon generation protocols. We situate our work in the context of other prior research on bespoke single
photon sources and networking including post-emission pulse shaping, temporal gating and cavity-based methods. In comparison, our free-space process has greater flexibility in producing any waveform, requires less infrastructure, and can be readily applied across a wide range of
quantum emitters. We discuss the applications and limits of this technique, including how increasing
photon emission probabilities affects achievable temporal-mode overlap fidelities between emitted and target
photon waveforms.
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Quantum Physics
Random purification channel made simple
Filippo Girardi, Francesco Anna Mele and Ludovico Lami
The recently introduced random purification channel, which converts $n$ i.i.d. copies of any mixed
quantum state into a uniform convex combination of $n$ i.i.d. copies of its purifications, has proved to be an extremely useful tool in
quantum learning theory. Here we give a remarkably simple construction of this channel, making its known properties – and several new ones – immediately transparent. In particular, we show that the channel also purifies non-i.i.d. states: it transforms any permutationally symmetric state into a uniform convex combination of permutationally symmetric purifications, each differing only by a tensor-product
unitary acting on the purifying system. We then apply the channel to give a one-line proof of (a stronger version of) the recently established Uhlmann's
theorem for
quantum divergences.
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Quantum Physics
Quantum Polymorphisms and the Complexity of Quantum Constraint Satisfaction
Lorenzo Ciardo, Gideo Joubert and Antoine Mottet
We introduce the concept of
quantum polymorphisms to the complexity theory of
quantum constraint satisfaction. Via this notion, we build an algebraic framework of reductions between
quantum CSPs, and we establish a Galois connection between
quantum polymorphism minions and
quantum relational constructions. By leveraging a contextuality property of
quantum polymorphisms, we fully characterise the existence of commutativity gadgets for relational structures, introduced by Ji as a method for achieving
quantum soundness of classical CSP reductions. Prior to our work, only a partial classification was known for a subclass of Boolean
languages and for non-Boolean
languages meeting specific structural conditions [Culf–Mastel, FOCS'25]. As an application of our framework, we prove that the
quantum CSPs parameterised by odd cycles and the
quantum CSP expressing
quantum satisfiability of Siggers clauses are undecidable.
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Quantum Physics
A Heuristic for Matrix Product State Simulation of Out-of-Equilibrium Dynamics of Two-Dimensional Quantum Spin Systems
Salvatore Mandrà, Brayden Ware, Nikita Astrakhantsev et al. (+4 more)
Out-of-
equilibrium dynamics of non-integrable
Hamiltonian many-body
quantum systems are characterized by highly entangled wave functions. Near-maximal
entanglement arises in systems exhibiting thermalization or pre-thermalization, where the system converges to a steady state with a fixed energy density. Classical simulation of the time dependence of such wave functions requires exponential resources. However, typical computations aim to estimate expectation values of local operators and correlation functions to some expected precision. For thermalizing systems at sufficiently high energy densities, such computations can be done without storing the full wave function by instead simulating the
evolution of the local operator, which requires significantly fewer resources. Nonetheless, constructing such resource-efficient classical
algorithms remains a challenge for intermediate energy densities, where simulating both the wave function and operator
evolution is costly. In this paper, we propose a heuristic approach to accelerate the convergence of
Matrix Product State (MPS) simulations of expectation values, applicable across a broad range of energy densities. We estimate the desired observables by rescaling the MPS results at low bond dimensions with a factor that depends on the fidelity of the MPS wave function. Using this technique, we simulated the dynamics of the two-dimensional Transverse-Field Ising Model (TFIM) on a $7\times8$ grid with periodic boundary conditions, using a maximum bond dimension of $\chi = 4096$ on a single A100 GPU, as well as the dynamics of the two-dimensional XY model on grids of size up to $9\times9$. We compare our TFIM results to similar simulations on a digital
quantum processor [R. Haghshenas et al., Nature 653, 56 (2026)], demonstrating excellent agreement and confirming the predictive power of our method.
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All authors Salvatore Mandrà, Brayden Ware, Nikita Astrakhantsev, Sergei Isakov, Benjamin Villalonga, Tom Westerhout, Kostyantyn Kechedzhi
Quantum Physics
COMPAS: A Distributed Multi-Party SWAP Test for Parallel Quantum Algorithms
Brayden Goldstein-Gelb, Kun Liu, John M. Martyn et al. (+3 more)
The limited number of
qubits per chip remains a critical bottleneck in
quantum computing, motivating the use of distributed architectures that interconnect multiple
quantum processing units (QPUs). However, executing
quantum algorithms across distributed systems requires careful co-design of algorithmic primitives and hardware architectures to manage
circuit depth and
entanglement overhead. We identify multivariate trace estimation as a key subroutine that is naturally suited for distribution, and broadly useful in tasks such as estimating Rényi
entropies, virtual cooling and
distillation, and certain applications of
quantum signal processing. In this work, we introduce COMPAS, an architecture that realizes multivariate trace estimation across a multi-party network of interconnected modular and distributed QPUs by leveraging pre-shared entangled Bell pairs as resources. COMPAS adds only a constant depth overhead and consumes Bell pairs at a rate linear in
circuit width, making it suitable for near-term hardware. Unlike other schemes, which must choose between asymptotic optimality in
circuit depth or GHZ width, COMPAS achieves both at once. Additionally, we analyze network-level errors and simulate the effects of
circuit-level noise on the architecture.
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All authors Brayden Goldstein-Gelb, Kun Liu, John M. Martyn, Hengyun Zhou, Yongshan Ding, Yuan Liu
Quantum Physics
The Boundary Time Crystal as a light source for collectively enhanced sensing
Malik Jirasek, Igor Lesanovsky and Albert Cabot
Modern precision measurements, such as interferometry for detecting gravitational waves, rely on the estimation of optical phases encoded in light fields. Here, we propose to exploit the collectively enhanced output field of a driven-dissipative many-body
quantum system as a light source in order to improve the precision of estimating optical phases. Pronounced temporal correlations of such output fields benefit the sensitivity of measurement protocols, which we show theoretically by employing a boundary time
crystal as a light source. The fundamental bound on the precision of such estimation shows scaling with the number of constituents $N$ of the many-body system as $N^4$ while scaling linearly with the measurement time $T$. We discuss this scaling both from a perspective of the resources employed to build the light source and of the resources produced by the light source. We show that a measurement scheme, in which the phase shifted light field is guided into an auxiliary replica system, which serves as a detector that is sensitive to non-trivial temporal correlations of light, can saturate the fundamental bound on precision at an optimal operating point.
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Quantum Physics · Cross-listed from cs.IT
Quantum Private Distributed Matrix Multiplication: Extending the Classical Codes and Limitations
Mohamed Nomeir, Alptug Aytekin, Lei Hu et al. (+1 more)
In this paper, we explore how
quantum resources can be used to increase the rate of private distributed
matrix multiplication (PDMM). In PDMM, a user who has two high-dimensional
matrices, A and B, and lacks the computational capabilities to apply
matrix multiplication locally, divides the
matrices A and B into K and L sub-blocks, respectively. Then, the user sends them to N servers to apply the required multiplication privately, i.e., any $T$ colluding servers cannot get any information about the user's
matrices. The goal is to reduce the number of servers needed to perform the required
matrix multiplication, thereby decreasing the communication cost. First, in the high-
privacy regime, the state-of-the-art classical code is called the gap additive secure
polynomial (GASP) code. We define a feasibility requirement in the
quantum setting for the GASP code such that the highest performance is achieved when the requirement is satisfied. Thus, super-dense coding gain is achieved when the feasibility condition is satisfied. We show that when $T \geq KL-K+1$, the feasibility condition is always satisfied and the GASP code can be extended to the
quantum version. In the case of $T < KL-K+1$, the feasibility can still be satisfied. To further examine this behavior, we numerically study how the minimum
privacy requirement depends on the
matrix dimensions and provide a quadratic estimate for this relation. The results suggest that feasibility can be achieved when $T \sim 0.5 KL$. Second, in the low-
privacy regime, the recently developed cyclic-addition degree tables (CAT) and discretely optimized GASP (DOG) codes are among the most efficient known classical constructions for PDMM. We show that the feasibility condition developed for GASP can be adopted for both CAT and DOG codes as well, thus unifying the feasibility framework for multiple classical PDMM coding schemes.
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All authors Mohamed Nomeir, Alptug Aytekin, Lei Hu, Sennur Ulukus
Quantum Physics
Persistence of Quantum Triality Relations in Open Qubit and Qutrit Systems
Pratidhwani Swain, Ramita Sarkar, Sukanta K. Tripathy et al. (+1 more)
We examine the complementarity among coherence (visibility), predictability, and
entanglement for
qubit and qutrit systems subjected to noisy
quantum channels. Using the system-path
entanglement framework, analytical expressions for all three quantities are derived for two- and three-slit interferometric setups. The study first establishes the validity of the triality relation in ideal conditions and then investigates its behavior under amplitude and phase damping. We find that amplitude damping redistributes coherence and population imbalance without violating complementarity, while phase damping reduces coherence but leaves predictability unchanged. These results demonstrate that the complementarity relation remains preserved even in open
quantum systems, highlighting its robustness against decoherence and providing a unified analytical understanding of noisy
quantum interferometry in low-dimensional systems.
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All authors Pratidhwani Swain, Ramita Sarkar, Sukanta K. Tripathy, Prasanta K. Panigrahi
Quantum Physics
Renormalisation of Fermionic Cellular Automata
Lorenzo Siro Trezzini, Andrea Pizzamiglio, Alessandro Bisio et al. (+1 more)
We present an exact renormalisation scheme for fermionic cellular automata on hypercubic
lattices. By grouping neighbouring
cells into tiles and selecting subspaces within them, multiple
evolution steps on the original system correspond to a single step of an effective automaton acting on the subspaces. We derive a necessary and sufficient condition for renormalisability and fully characterise the renormalisation flow for two-
cell tiles and two time steps of nearest-neighbour fermionic automata on a chain of spinless modes, identifying all fixed points.
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All authors Lorenzo Siro Trezzini, Andrea Pizzamiglio, Alessandro Bisio, Paolo Perinotti
Quantum Physics
Hilbert space fragmentation in driven-dephasing Rydberg atom array
Tianyi Yan, Chun Hei Leung and Weibin Li
We investigate the onset and mechanism of
Hilbert space fragmentation (HSF) in a chain of strongly interacting Rydberg atoms subject to local dephasing. It is found that the emergence of multiple long-lived metastable states is fundamentally tied to HSF of the driven-dephasing Rydberg atom system. We demonstrate that the manifesting HSF is captured by a dephasing PXP model that supports multiple degenerate zero modes. These modes form disconnected, block-diagonal subspaces of maximally mixed states, which consist of many-body
spin states sharing the same
symmetry. A key result is the identification of the underlying
symmetry in the HSF, where conserved quantities in each subspace are defined by the consecutive double excitation addressing operator. Moreover, we show explicitly that the number of the fragmented
Hilbert space grows exponentially with the chain length, following a modified Fibonacci sequence. Our work provides insights into many-body dynamics under dynamical constraints and opens avenues for controlling and manipulating HSF in Rydberg atom systems.
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Quantum Physics
Bounded-Error Quantum Simulation via Hamiltonian and Lindbladian Learning
Tristan Kraft, Manoj K. Joshi, William Lam et al. (+11 more)
Analog
Quantum Simulators offer a route to exploring strongly correlated many-body dynamics beyond classical computation, but their predictive power remains limited by the absence of quantitative error estimation. Establishing rigorous uncertainty bounds is essential for elevating such devices from qualitative demonstrations to quantitative scientific tools. Here we introduce a general framework for bounded-error
quantum simulation, which provides predictions for many-body observables with experimentally quantifiable uncertainties. The approach combines
Hamiltonian and Lindbladian Learning–a statistically rigorous inference of the coherent and dissipative generators governing the dynamics–with the propagation of their uncertainties into the simulated observables, yielding confidence bounds directly derived from experimental data. We demonstrate this framework on trapped-ion
quantum simulators implementing long-range Ising interactions with up to 51 ions, and validate it where classical comparison is possible. We analyze error bounds on two levels. First, we learn an open-system model from experimental data collected in an initial time window of quench dynamics, simulate the corresponding master equation, and quantitatively verify consistency between theoretical predictions and measured dynamics at long times. Second, we establish error bounds directly from experimental measurements alone, without relying on classical simulation–crucial for entering regimes of
quantum advantage. The learned models reproduce the experimental
evolution within the predicted bounds, demonstrating quantitative reliability and internal consistency. Bounded-error
quantum simulation provides a scalable foundation for trusted analog
quantum computation, bridging the gap between experimental platforms and predictive many-body physics. The techniques presented here directly extend to digital
quantum simulation.
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All authors Tristan Kraft, Manoj K. Joshi, William Lam, Tobias Olsacher, Florian Kranzl, Johannes Franke, Lata Kh Joshi, Rainer Blatt, Augusto Smerzi, Daniel Stilck França, Benoît Vermersch, Barbara Kraus, Christian F. Roos, Peter Zoller
Quantum Physics · Cross-listed from gr-qc
Alessio Belfiglio, Roberto Franzosi and Orlando Luongo
We discuss some
entanglement features associated with cubic non-Gaussian perturbations in single-field inflationary scenarios. We adopt standard momentum-space techniques to show how multipartite
entanglement arises for inflationary perturbation modes, focusing on the dynamics of the comoving
curvature perturbation. In particular, we quantify
entanglement generation via the recently proposed
Entanglement Distance, which introduces a
geometric interpretation of
quantum correlations in terms of the Fubini-Study metric. In the continuum limit, we show that the
Entanglement Distance arising from displacement transformations is proportional to the total number of excitations in the
quantum state for cubic perturbations, thus providing an upper bound on the von Neumann
entanglement entropy of any reduced state compatible with such excitations. Within the interaction picture, we further observe that the
quantum correlations arising from cubic gravitational interactions are typically much larger than the standard squeezing contribution, in agreement with previous studies focusing on von Neumann
entropy generation across the Hubble horizon. We further show how the inflationary parameters affect the total amount of such correlations, highlighting in particular their dependence on the inflationary energy scales and the number of e-foldings during slow-roll.
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Quantum Physics · Cross-listed from cond-mat.quant-gas
Cyprien Daix, Pok Man Tam, Maxime Dixmerias et al. (+5 more)
Pauli's exclusion principle forces
fermions to occupy distinct
quantum states, creating a filled region of momentum space at low temperature, the
Fermi sea, whose
topology governs the system's response to perturbations and the nature of its correlation functions. Recent theory predicts that for non-interacting
fermions, the Euler characteristic of a $D$-dimensional
Fermi sea – the topological invariant that describes its shape – is encoded in its ($D$+1)-point density correlations. Here we experimentally demonstrate this connection in a two-dimensional degenerate gas of neutral $^{6}$Li atoms using single-atom-resolved imaging. By measuring three- and four-point connected density correlations in real space, we directly extract topological invariants of the underlying
Fermi sea, including the Euler characteristic. Our results are in remarkable agreement with ideal-gas predictions, despite the presence of sizeable interactions, and establish a new pathway for probing many-body
topology through correlation measurements.
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All authors Cyprien Daix, Pok Man Tam, Maxime Dixmerias, Joris Verstraten, Tim de Jongh, Bruno Peaudecerf, Charles L. Kane, Tarik Yefsah
Quantum Physics
Quantum Cubature Codes
Yaoling Yang, Andrew Tanggara, Tobias Haug et al. (+1 more)
Bosonic codes utilize the infinite-dimensional
Hilbert space of harmonic oscillators to encode
quantum information, offering a hardware-efficient approach to
quantum error correction. Designing these codes requires precise
geometric arrangements of
quantum states in the phase space. Here, we introduce
Quantum Cubature Codes (QCCs), a powerful and generalized framework for constructing bosonic codes based on superpositions of coherent states. This formalism utilizes cubature formulas from multivariate approximation theory, which connect the continuous geometry of the phase space to discrete, weighted point sets, ensuring the conditions for error correction are met. We demonstrate that this framework provides a unifying perspective, revealing that well-established codes, such as cat codes and the recently proposed
quantum spherical codes (QSCs), are specific instances of QCCs corresponding to uniform weights on a single energy shell. The QCC formalism unlocks a vast new design space, encompassing non-uniform superpositions and multi-shell configurations. We leverage this framework to discover several new families of codes derived from Euclidean designs, allowing for greater
geometric separation between logical states, which correlates with improved performance under
photon loss. Numerical simulations under a pure-loss channel show that our multi-shell QCCs can outperform their single-shell counterparts by maximizing
geometric separation with optimal energy at fixed pure-loss rate.
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All authors Yaoling Yang, Andrew Tanggara, Tobias Haug, Kishor Bharti
Quantum Physics
Inhibited radiative decay enhances single-photon emitters
Florian Burger, Stephan Rinner, Andreas Gritsch et al. (+2 more)
Quantum networks and modular
quantum computers require efficient
spin-
photon interfaces, often realized using optical resonators that enhance radiative decay on a desired transition. However, this requires small mode volumes and high quality factors, which limits multiplexing capacity and demands precise frequency tuning. Here, we demonstrate an alternative approach that circumvents these bottlenecks for upscaling. Using a W1 silicon photonic
crystal waveguide with a tailored photonic bandgap, we selectively inhibit unwanted decay pathways, thereby redirecting emission to the desired transition. This enables efficient
photon collection over a large frequency range, allowing the resolution and individual addressing of tens of erbium dopants. Their lifetimes are preserved, or even increased, compared to bulk material. The extended mode volume of the devices enables the use of lower dopant concentrations, thereby improving emitter coherence. Our approach can be combined with Purcell enhancement and applied to other
spin-
qubit platforms, opening intriguing perspectives for photonic
quantum technologies.
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All authors Florian Burger, Stephan Rinner, Andreas Gritsch, Kilian Sandholzer, Andreas Reiserer
Quantum Physics · Cross-listed from cond-mat.mes-hall
Exchange interaction in gate-defined quantum dots beyond the Hubbard model
Alexander Willmes, Patrick Bethke, M. Mohamed El Kordy Shehata et al. (+10 more)
A quantitative description of the exchange interaction in
quantum dots is relevant for modeling gate operations of
spin qubits. By measuring the amplitude and frequency of exchange-driven
qubit state oscillations, we measure the detuning dependence of the exchange coupling in a GaAs double
quantum dot over three orders of magnitude. Both 1D and 3D full configuration interaction simulations can replicate the observed behavior. Extending a Hubbard model by including excited states increases the range of detuning where it provides a good fit, thus elucidating the underlying physics.
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All authors Alexander Willmes, Patrick Bethke, M. Mohamed El Kordy Shehata, George Simion, M.A. Wolfe, Tim Botzem, Robert P.G. McNeil, Julian Ritzmann, Arne Ludwig, Andreas D. Wieck, Dieter Schuh, Dominique Bougeard, Hendrik Bluhm
Quantum Physics
Unrepeated White Rabbit Time Synchronisation over a 300 km Optical Fibre Link
Ben Amies-King and Marco Lucamarini
White Rabbit (WR) technology provides a commercially-available off-the-shelf solution for time synchronisation with sub-nanosecond accuracy and picosecond-level precision over optical fibre links typically spanning tens of kilometres. Such high-performance time dissemination can support a variety of applications, including position,
navigation and timing (PNT), financial transactions, metrology, as well as
entanglement and
quantum key distribution (QKD). Demonstrations of WR over significantly longer distances remain few and far between, particularly in scenarios where intermediate amplification is unavailable, such as stretches of long-haul
underwater fibre. In this work, we report the longest unrepeated deployment of WR to date, achieving time synchronisation over a 300 km (51.34 dB) single-span optical fibre link, even in highly asymmetrical configurations, with 99.86% uptime, whilst maintaining picosecond-level precision and sub-nanosecond accuracy. This was achieved through careful selection and optimisation of the components deployed at the link's end points. By leveraging standard telecom fibre and off-the-shelf hardware, our results pave the way for a scalable and standardised timing backbone for large-scale
quantum networks, offering a practical route toward time distribution in future heterogeneous
quantum communication systems.
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Quantum Physics · Cross-listed from physics.atom-ph
A permanent-magnet Zeeman slower and magneto-optical trap for calcium atoms for ultracold Rydberg physics
Eduardo Marin-Bujedo, Julien A. L. Grondin, Thomas Schiltz et al. (+3 more)
We report the construction and characterization of an experimental setup for producing a cold gas of $^{40}$Ca atoms and excite them to high Rydberg states with a resonant three-
photon-excitation scheme. The apparatus comprises four stages, each designed in-house. An oven heated to $\sim 500^\circ$C generates an atomic beam that is collimated by a capillary stack. The beam is sent into a passive, permanent-magnet-based Zeeman slower that reduces the atomic velocity to $30$ m/s. The slow atoms are captured in a magneto-optical trap (MOT) and cooled to $1.0(3)$ mK with a trapping time of $16(2)$ ms. Ground-state atoms in the cold gas are excited to high Rydberg states via resonant excitation through the intermediate $4s4p\, ^1P_1$ and $4s4d\, ^1D_2$ states. The MOT is operated at the center of an electrode stack, which serves to apply continuous and pulsed electric fields and field-ionize the Rydberg atoms for detection. We
benchmark our MOT against previous implementations and find its performance consistent with state-of-the-art results in terms of temperature and trapping lifetime. Finally, we demonstrate Rydberg spectroscopy of calcium, confirming the system's suitability for ultracold Rydberg physics experiments.
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All authors Eduardo Marin-Bujedo, Julien A. L. Grondin, Thomas Schiltz, Thomas Corbo, Xavier Urbain, Matthieu Génévriez
Quantum Physics
Identifying genuine entanglement of lossy noisy very large scale continuous variable Greenberger-Horne-Zeilinger state
Xiao-yu Chen
Genuine
entanglement identification of large scale systems is crucial for
quantum computation,
quantum communication and
quantum learning advantage. In contrast to experiments, where noisy intermediate-scale programmable photonic
quantum processors have been developed, theoretically very limited results have been achieved for detecting genuine
entanglement of continuous variable multipartite systems. We propose a quite general and efficient
entanglement detection framework for all kinds of multipartite
entanglement of continuous variable systems based on uncertainty relations and the sign
matrix technique.
Matrix criteria are demonstrated and can be applied to various
entanglement depth and k-separability problems of multimode systems. We illustrate the genuine
entanglement conditions of continuous variable Greenberger-Horne-Zeilinger states of more than a hundred million modes in a
photon loss and noise environment.
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Quantum Physics
Systems that saturate the Margolus-Levitin quantum speed limit
Ole Sönnerborn
We provide a complete characterization of all finite-dimensional
quantum systems that saturate the Margolus-Levitin
quantum speed limit at arbitrary Uhlmann-Jozsa fidelity. Employing a purification-based approach, we prove that mixed-state saturation occurs precisely when three structural criteria are fulfilled: the state's support is confined to the sum of two energy eigenspaces (the ground level and a single excited level); each eigenvector of the state with nonzero weight is a fixed superposition of one ground- and one excited-state energy eigenvector (determined by the minimizer of the objective function identified by Giovannetti et al.) and all such eigenvectors evolve in mutually orthogonal subspaces. These requirements impose a strict rank bound, ruling out saturation by any faithful state. For
quantum bits, we derive a purity-resolved and tight Margolus-Levitin bound that reduces to the pure-state result in the limit of unit purity. Through a time-reversal argument, we further extend the dual Margolus-Levitin
quantum speed limit to mixed states and establish the corresponding saturation conditions.
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