The discovery of topological features quantum states plays an important role in modern condensed matter physics and various artificial systems. Due to the absence local order parameters, detection phase transitions remains a challenge. Machine learning may provide effective methods for identifying features. In this work, we show that unsupervised manifold can successfully retrieve momentum real space. Our results Chebyshev distance between two data points sharpens characteristic space, while...

We implement an all-optical setup demonstrating kernel-based quantum machine learning for two-dimensional classification problems. In this hybrid approach, kernel evaluations are outsourced to projective measurements on suitably designed states encoding the training data, while model is processed a classical computer. Our two-photon proposal encodes data points in discrete, eight-dimensional feature Hilbert space. order maximize application range of deployable kernels, we optimize maps...

Autonomous quantum error correction (AQEC) protects logical qubits by engineered dissipation and thus circumvents the necessity of frequent, error-prone measurement-feedback loops. Bosonic code spaces, where single-photon loss represents dominant source error, are promising candidates for AQEC due to their flexibility controllability. While existing proposals have demonstrated in-principle feasibility with bosonic these schemes typically based on exact implementation Knill-Laflamme...

The incoherent dynamical properties of open quantum systems are generically attributed to an ongoing correlation between the system and its environment. Here, we propose a novel way assess nature these system-environment correlations by examining dynamics alone. Our approach is based on possibility or impossibility simulate open-system with Hamiltonian ensembles. As show, such (im)possibility closely linked correlations. We thus define nonclassicality in terms nonexistence...

We study the functional renormalization group flow of a Higgs-Yukawa toy model mimicking top-Higgs sector standard model. This approach allows for treating arbitrary bare couplings. For class potentials \phi^4-type at given ultraviolet cut-off, we show that finite infrared Higgs mass range emerges naturally from itself. masses outside resulting bounds cannot be connected to any conceivable set parameters in this standard-model \phi^4 class. By contrast, more general allow diminish lower...

One of the central problems in quantum theory is to characterize, detect, and quantify quantumness terms classical strategies. Dephasing processes, caused by non-dissipative information exchange between systems environments, provides a natural platform for this purpose, as they control quantum-to-classical transition. Recently, it has been shown that dephasing dynamics itself can exhibit (non)classical traits, depending on nature system-environment correlations related (im)possibility...

We discuss topology in dissipative quantum systems from the perspective of trajectories. The latter emerge unraveling Markovian master equations and/or continuous measurements. Ensemble-averaging trajectories at occurrence jumps, i.e., jump times, gives rise to a discrete, deterministic evolution which is highly sensitive presence dark states [Gneiting et al., Phys. Rev. A 104, 062212 (2021)]. show for broad family translation-invariant collapse models that set dark-state-inducing...

Solving the ground state and ground-state properties of quantum many-body systems is generically a hard task for classical algorithms. For family Hamiltonians defined on an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>m</a:mi></a:math>-dimensional space physical parameters, its at arbitrary parameter configuration can be predicted via machine learning protocol up to prescribed prediction error <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>ɛ</b:mi></b:math>,...

Gottesman-Kitaev-Preskill (GKP) encoding holds promise for continuous-variable fault-tolerant quantum computing. While an ideal GKP is abstract and impractical due to its nonphysical nature, approximate versions provide viable alternatives. Conventional codewords are superpositions of multiple large-amplitude squeezed coherent states. This feature ensures correctability against single-photon loss dephasing at short times, but also increases the difficulty preparing codewords. To minimize...

Frustration, that is, the impossibility of satisfying energetic preferences between all spin pairs simultaneously, underlies complexity many fundamental properties in systems, including computational difficulty determining their ground states. Coherent Ising machines (CIMs) have been proposed as a promising analog approach to efficiently find different degenerate states large and complex models. However, CIMs also face challenges solving frustrated models: frustration not only reduces...

A progressive loss of phase information (i.e., decoherence) is fundamental to many physical systems since they evolve over time. Researchers present a way deriving master equations dynamically characterize disordered quantum with finite dimensions.

A scheme for quantum state tomography based on an efficient neural network representation is demonstrated. The method, tailored to a relevant class of nearly pure states, or simple mixed was tested using experimental data from trapped-ion experiments with four eight qubits.

We discuss an experimentally amenable class of two-particle states motion giving rise to nonlocal spatial interference under position measurements. Using the concept modular variables, we derive a separability criterion which is violated by these non-Gaussian states. While focus on free material particles, presented results are valid for any pair canonically conjugate continuous variable observables and should apply variety bipartite phenomena.

We study to what extent the detrimental impact of dissipation on quantum properties can be compensated by suitable coherent dynamics. To this end, we develop a general method determine control Hamiltonian that optimally counteracts given mechanism, in order sustain desired property, and apply it two exemplary target properties: coherence decaying two-level system, entanglement qubits presence local dissipation.

The theory of optimal quantum control serves to identify time-dependent Hamiltonians that efficiently produce desired target states. As such, it plays an essential role in the successful design and development technologies. However, often delivered pulses are exceedingly sensitive small perturbations, which can make hard if not impossible reliably deploy these experiments. Robust aims at mitigating this issue by finding uphold their capacity reproduce states even presence pulse...

Flatbands feature the distortion-free storage of compact localized states tailorable shape. Their reliable sojourn is, however, limited by disorder potentials, which generically cause uncontrolled coupling into dispersive bands. We find that, while detuning flatband from band intersections suppresses their direct decay bands, disorder-induced state distortion causes a delayed, dephasing-mediated decay, lifting static nature and setting finite lifetime for sojourn. exemplify this generic,...

Non-Gaussian continuous-variable states play a central role both in the foundations of quantum theory and for emergent technologies. In particular, ``cat states,'' i.e., two-component macroscopic superpositions, embody coherence an accessible way can be harnessed fundamental tests information tasks alike. Degenerate optical parametric oscillators naturally produce single-mode cat thus represent promising platform their realization harnessing. We show that dissipative coupling between...

We derive a quantum master equation which describes the dynamics of ensemble-averaged state homogeneous disorder models at short times, and mediates transition from coherent superpositions into classical mixtures. While each single realization follows unitary dynamics, this decoherencelike behavior arises as consequence ensemble average. The manifestly reflects translational invariance correlations allows us to relate disorder-induced collisional decoherence process, where determine spatial...

We present a scheme to establish nonclassical correlations in the motion of two macroscopically separated massive particles without resorting entanglement their internal degrees freedom. It is based on dissociation diatomic molecule with temporally Feshbach pulses generating motional state counterpropagating atoms that capable violating Bell inequality by means correlated single-particle interferometry. evaluate influence dispersion correlation, showing it be important but manageable...

We extend the Wigner-Weyl-Moyal phase-space formulation of quantum mechanics to general curved configuration spaces. The underlying phase space is based on chosen coordinates manifold and their canonically conjugate momenta. resulting Wigner function displays axioms a quasiprobability distribution, any Weyl-ordered operator gets associated with corresponding function, even in absence continuous symmetries. Liouville equation reduces classical semiclassical limit. demonstrate formalism for...

The active harnessing of quantum resources in engineered devices poses unprecedented requirements on device control. Besides the residual interaction with environment, causing environment-induced decoherence, uncontrolled parameters system itself---disorder---remain as a substantial factor limiting precision and thus performance devices. These perturbations may arise, for instance, due to imperfect sample production, stray fields, or finite accuracy control electronics. Disorder-dressed...

We introduce jump-time unraveling as a distinct description of open quantum systems. As our starting point, we consider jump trajectories, which emerge, physically, from continuous measurements, or, formally, the Markovian master equations. If stochastically evolving trajectories are ensemble-averaged at specific times, resulting states solutions to associated equation. demonstrate that can also be counts. The jump-time-averaged then discrete, deterministic evolution equation, with time...

We investigate to what extent a suitably chosen system Hamiltonian can counteract local dissipative processes and preserve entanglement in the stationary state. The results determine prospects limitations of state preparation schemes based on natural -- contrast engineered, typically non-local schemes. As an exemplary case, we two spontaneously decaying two-level systems with optimal properties. corresponding is derived, its possible experimental implementation discussed detail. Finally,...

We critically evaluate the most widespread assumption in theoretical description of coherent control strategies for open quantum systems. show that, non-Markovian systems dynamics, this fixed-dissipator leads to a serious pitfall generally causing difficulties effective modeling controlled system. that at present, avoid these problems, full microscopic system presence noise may often be necessary. illustrate our findings with paradigmatic example.