arXiv subjects

Jarosław K. Korbicz

Publications and source records attributed to Jarosław K. Korbicz.

At least 19 recordsLinked to original sources

arXiv2026

White paper: 1-10 Hz matter-wave interferometer to test the spin entanglement witness for quantum gravity

In this white paper, we highlight the importance of the ($1-10~{\rm Hz}$) frequency range for laboratory tests of the quantum nature of gravity using the quantum gravity-induced entanglement of masses (QGEM) protocol. QGEM requires matter-wave interferometers with masses ($m\sim10^{-15}-10^{-14}~{\rm kg}$), brought within separations ($d\sim30-50~μ{\rm m}$), while maintaining spatial superpositions of ($1-20~μ{\rm m}$) and coherence for ($τ\sim 0.1 - 1~{\rm s}$). These requirements make low-frequency environmental noise a central experimental challenge and place QGEM in a regime closely related to the low-frequency goals of the Einstein Telescope (ET) and the Cosmic Explorer (CE). In particular, QGEM is sensitive to relative acceleration noise (RAN) and to gravity-gradient noise (GGN) generated by seismic and other environmental mass-density fluctuations. For representative parameters $m=10^{-14}~{\rm kg}$, $Δx=10~μ{\rm m}$, and $τ=1~{\rm s}$, the differential acceleration-noise amplitude spectral density must be suppressed well below the $10^{-15}~{\rm m\,s^{-2}/\sqrt{Hz}}$ level to keep acceleration-induced dephasing below the relevant experimental scale. Achieving this level of low-frequency noise suppression is therefore a key requirement for QGEM and closely parallels the seismic and gravity-gradient noise challenges that ET and CE address.

quant-ph↗

arXiv2026

Gottesman-Kitaev-Preskill error-correction with decohered resources

Teleportation-based Gottesman-Kitaev-Preskill (GKP) error correction typically assumes a decoherence-free GKP ancilla Bell pair, an idealization that is difficult to reconcile with the ubiquitous environmental decoherence in bosonic systems. Here, we analyze the performance of the GKP protocol subject to pure-dephasing processes, ubiquitous in realistic situations. We show that, under this class of interactions, teleportation, instead of projecting the input onto the GKP subspace, transforms GKP error correction into a correlated Pauli-Gaussian noise process that can accumulate over successive correction rounds. Thus, unlike in previously studied noisy GKP scenarios, the code no longer self-corrects. Moreover, repeated noisy GKP teleportation drives the encoded modes out of the logical subspace, progressively degrading the encoded codewords. We show that the resulting leakage rapidly saturates with the number of correction rounds. Finally, we investigate the implications of our results for motional-oscillator-based GKP error-correction platforms.

quant-ph↗

arXiv2026

Closing objectivity loophole in Bell tests on a public quantum computer

We have constructed and run a Bell test of local realism focusing on the objectivity criterion. Objectivity means that the outcomes are confirmed macroscopically by a few observers at each party. The IBM Quantum and IonQ devices turn out to be sufficiently accurate to pass such an extended Bell-type test, although at the price of communication loopholes and residual but statistically significant signaling. The test also serves as the benchmark of entanglement spread across larger sets of qubits.

quant-ph↗

arXiv2026

Port-based teleportation under pure-dephasing decoherence

We study deterministic port based teleportation in the presence of noise affecting both the entangled resource state and the measurement process. We focus on a physically motivated model in which each Bell pair constituting the resource interacts with an identical local environment, corresponding to independently distributed entangled links. Two noisy scenarios are analyzed: one with decoherence acting solely on the resource state and ideal measurements, and another with noisy, noise adapted measurements optimised for the given noise model. In the first case, we derive an analytical lower bound and later a closed-form expression for the entanglement fidelity of the teleportation channel and analyze its asymptotic behaviour. In the second, we combine semi analytical and numerical methods. Surprisingly, we find that noise-adapted measurements perform worse than the noiseless ones. To connect the abstract noise description with microscopic physics, we embed the protocol in a spin boson model and investigate the influence of bath memory and temperature on the teleportation fidelity, highlighting qualitative differences between different environments.

quant-ph↗

arXiv2026

Contextual advantage implies limited distinguishability in any physical theory

A central question in quantum information is whether a given set of states can provide an advantage in some information-processing task. We establish a universal connection between two such questions: how well a set of states can be discriminated, and whether it can power tasks whose advantage stems from generalized contextuality. Working in the framework of generalized probabilistic theories (GPTs), which includes quantum and classical systems as special cases, we show that any set of states able to provide a nonclassical advantage in a contextuality-powered task must obey nontrivial upper bounds on the success probability of every state discrimination task using the full set. Contextual advantage therefore implies limited distinguishability, exposing a trade-off between two basic operational resources. Importantly, this is more than a statement about the idealized limit: perfect distinguishability is not needed to preclude contextuality. Our thresholds lie strictly below unity, so any set whose discrimination performance exceeds them while still imperfectly distinguishable is already guaranteed to admit a noncontextual explanation. The bounds follow from a simple geometric property, linear dependence of the state set, take a closed analytical form, and depend only on the prior of the task and the convex geometry of the states. As an illustration, we apply them to generalized parity-oblivious multiplexing, where sufficiently high success in the task implies that at least one sub-ensemble of the codebook cannot power any contextual advantage.

quant-ph↗

arXiv2026

Decoherence without the state: A causal quantum Darwinist approach

The consistent histories formalism can be used to describe histories comprised of events across many systems, times, and places, plausibly rich enough to describe our experiences of the classical world; however, many consistent history sets are nonclassical and thus not obviously relevant to our experiences. Meanwhile, the program of environmentally induced decoherence identifies dynamically privileged classical degrees of freedom, but provides no general account of when or how many such degrees of freedom consistently combine to form histories. This work shows that the strengths of these two approaches can be combined by adopting a dynamics-first perspective on decoherence. Inspired by quantum causal models and quantum Darwinism, we define the process of decoherence in terms of the causal influences through unitary dynamics required for the proliferation of information about observables. We characterise decoherence as a property of the unitary dynamics, without presupposing the existence of any quantum state. Instead, we show that the state emerges from dual decoherence, related to decoherence by time-reversal of the unitary dynamics. Indeed, for any set of systems in an arbitrary unitary circuit, decoherence and its dual single out a privileged consistent history set -- and we demonstrate through examples that states emerge from dual decoherence while outcomes emerge from decoherence. Hence the idea that quantum states emerge from the process of decoherence turns out to be the key missing ingredient for unifying environmentally induced decoherence and consistent histories. Taking this idea ontologically seriously leads to a recently proposed causal interpretation of quantum theory or a dynamics-first version of the Everett interpretation. The causal approach also sheds light on the suppression of off-diagonal terms, time asymmetry, and robustness of the pointer basis.

quant-ph↗

arXiv2025

Coherence-Assisted Entanglement Activation During Open Evolution

The fact that in the course of an open evolution there is, in a vast majority of cases, the creation of system-environment entanglement out of the initial coherence, has been known for many years. However, how much entanglement can be created under general assumptions has not been analyzed yet. In this work, we investigate system-environment entanglement generation under a broad and important class of interactions known as pure dephasing interactions and for arbitrary initial conditions. Our main results are the following bounds on the relative entropy of entanglement $E_r(σ_{SE})$ after evolution: $ C_r(ρ_S) - H(\mathcal{I}|\mathcal{M}) \leq E_r(σ_{SE}) \leq C_r(ρ_S) - C_r(σ_S) + H(\mathcal{I})$, connecting it on one side to the initial relative entropy of coherence, $C_r(ρ_S)$, and information extractable from the environment, $H(\mathcal{I}|\mathcal{M})$, and on the other side to the decoherence strength, $ C_r(ρ_S) - C_r(σ_S)$, making quantitatively precise the statement that larger entanglement leads to more decoherence. As an illustration, we apply our results to the spin-boson model, where a qubit interacts with a bosonic bath, showing time evolution of the entanglement and the Markovian/non-Markovian crossover. Our results help better understand and quantify the complicated correlations, produced during an open evolution, which will hopefully lead to better and new decoherence mitigation techniques.

quant-ph↗

arXiv2025

Towards objectivity of classical reference frames in quantum mechanics

Recent advances in our understanding of foundations of quantum mechanics have shown that information can be made objective through quantum states. Such objectification processes, predicted e.g. in a variety of quantum open systems, must accompany any realistic quantum-to-classical transition mechanism in order to reproduce the objective character of the classical limit of our world. However, so far only examples of simple, unstructured information, such as a value of an observable, have been studied. In this work we show that a more complicated form of information, given by a Cartesian reference frame, can also be made (at least partially) objective in quantum mechanics. The non-trivial internal gauge structure of reference frames, given by the transformation group, leads to a more general form of objectivity, where all observers see the same but modulo their relative orientations, like it happens in modern understanding of geometry. This opens a way to extend quantum objectivity beyond simple scenarios and possibly link it to the foundations of modern geometry.

quant-ph↗

arXiv2024

Holevo bound and objectivity in the boson-spin model

Emergence of objective, classical properties in quantum systems can be described in the modern language of quantum information theory. In this work, we present an example of such an analysis. We apply the quantum channel theory to a boson-spin model of open quantum systems and calculate, using recoilless approximation and the Floquet theory, the Holevo quantity, which bounds the capacity of the channel, broadcasting information about the central system into its environment. We analyze both the short-time regime, showing quadratic in time initial growth of the capacity, and the asymptotic regime. Complicated dependence on the model parameters, such as temperature, tunneling energy for the environment, etc., is also analyzed, showing, e.g., regimes where the Holevo bound reaches its maximum.

quant-ph↗

arXiv2024

Encoding position by spins: Objectivity in the boson-spin model

We investigate quantum objectivity in the boson-spin model, where a central harmonic oscillator interacts with a thermal bath of spin-1/2 systems. We analyze how information about a continuous position variable can be encoded into discrete, finite-dimensional environments. More precisely, we study conditions under which the so-called Spectrum Broadcast Structures (SBS) can be formed in the model. These are multipartite quantum state structures, representing a mode-refined form of decoherence. Working in the recoil-less limit, we use the Floquet theory to show that despite its apparent simplicity, the model has a rich structure with different regimes, depending on the motion of the central system. In one of them, the faithful encoding of the position and hence objectivity are impossible irrespectively of the resources used. In other, large enough collections of spins will faithfully encode the position information. We derive the characteristic length scales, corresponding to decoherence and precision of the encoding.

quant-ph↗

arXiv2024

Complementarity between decoherence and information retrieval from the environment

We address the problem of fundamental limitations of information extraction from the environment in open quantum systems. We derive a model-independent, hybrid quantum-classical solution of open dynamics in the recoil-less limit, which includes environmental degrees of freedom. Specifying to the celebrated Caldeira-Leggett model of hot thermal environments, ubiquitous in everyday situations, we reveal the existence of a new lengthscale, called distinguishability length, different from the well-known thermal de Broglie wavelength that governs the decoherence. Interestingly, a new integral kernel, called Quantum Fisher Information kernel, appears in the analysis. It complements the well-known dissipation and noise kernels and satisfies disturbance-information gain type of relations, similar to the famous fluctuation-dissipation relation. Our results complement the existing treatments of the Caldeira-Legget model from a non-standard and highly non-trivial perspective of information dynamics in the environment. This leads to a full picture of how the open evolution looks like from both the system and the environment points of view, as well as sets limits on the precision of indirect observations.

quant-ph↗

arXiv2023

Gaussian work extraction from random Gaussian states is nearly impossible

Quantum thermodynamics can be naturally phrased as a theory of quantum state transformation and energy exchange for small-scale quantum systems undergoing thermodynamical processes, thereby making the resource theoretical approach very well suited. A key resource in thermodynamics is the extractable work, forming the backbone of thermal engines. Therefore it is of interest to characterize quantum states based on their ability to serve as a source of work. From a near-term perspective, quantum optical setups turn out to be ideal test beds for quantum thermodynamics; so it is important to assess work extraction from quantum optical states. Here, we show that Gaussian states are typically useless for Gaussian work extraction. More specifically, by exploiting the ``concentration of measure'' phenomenon, we prove that the probability that the Gaussian extractable work from a zero-mean energy-bounded multimode random Gaussian state is nonzero is exponentially small. This result can be thought of as an $ε$-no-go theorem for work extraction from Gaussian states under Gaussian unitaries, thereby revealing a fundamental limitation on the quantum thermodynamical usefulness of Gaussian components.

quant-ph↗

arXiv2023

Pointer States in the Born-Markov approximation

Explaining the emergence of classical properties of a quantum system through its interaction with the environment has been one of the promising ideas on how to understand the notorious quantum-to-classical transition. A pivotal role in this approach is played by, so called, pointer states which are quantum states least affected by the environment and are ``carriers" of classical behavior. We develop here a general method on how to find pointer states. Working within the Born-Markov approximation, we combine methods of group theory and open quantum systems to derive explicit equations describing pointer states. They contain variances squared of certain operators, thus resembling the defining equations of coherent states, but are in general different from the latter. This shows that two notions of being ``the closest to the classical" -- one defined by the uncertainty relations and the other by the interaction with the environment -- are in general different. As an example, we study arbitrary spin-$J$ systems interacting with bosonic or spin thermal environments and find explicitly pointer states for $J=1$.

quant-ph↗

arXiv2023

Purifying teleportation

Coupling to the environment typically suppresses quantum properties of physical systems via decoherence mechanisms. This is one of the main obstacles in practical implementations of quantum protocols. In this work we show how decoherence effects can be reversed/suppressed during quantum teleportation in a network scenario. Treating the environment quantumly, we show that under a general pure dephasing coupling, performing a second teleportation step can probabilistically reverse the decoherence effects if certain commutativity conditions hold. This effect is purely quantum and most pronounced for qubit systems, where in 25 % of instances the decoherence can be reversed completely. As an example, we show the effect in a physical model of a qubit register coupled to a bosonic bath. We also analyze general $d$-dimensional systems, identifying all instances of decoherence suppression. Our results are proof-of-concept but we believe will be relevant for the emerging field of quantum networks as teleportation is the key building block of network protocols.

quant-ph↗

arXiv2021

Universal structure of objective states in all fundamental causal theories

A crucial question is how objective and classical behavior arises from a fundamental physical theory. Here we provide a natural definition of a decoherence process valid in all causal theories, and show how its behavior can be extremely different from the quantum one. Remarkably, despite this, we prove that the so-called spectrum broadcast structure characterizes all objective states in every fundamental causal theory, exactly as in quantum mechanics. Our results show a stark contrast between the extraordinarily diverse decoherence behavior and the universal features of objectivity.

quant-ph↗

arXiv2021

Decoherence and objectivity in higher spin environments

We analyze decoherence and objectivization processes in spin-spin models for arbitrary spins. We first derive the most general analytic form of the decoherence factor in the measurement limit, where the interaction Hamiltonian dominates the rest. We then analyze thermal environments and derive exact, analytic formulas for both the decoherence factor and the state fidelity of post-interaction environment states. This allows to analyze the objectivization process of the state of the central spin during the interaction. We do so using, so called, Spectrum Broadcast Structures (SBS), which are specific multipartite quantum states encoding a certain operation notion of objectivity. We analyze analytically (for short times) and numerically how higher spin influences the efficiency of decoherence and objectivization processes. As expected, the higher the spin of the environment, the more efficient decoherence and objectivization become. This work is a generalization of previous studies, limited to spin-$1/2$ systems only, and we hope will be useful in future objectivity experiments.

quant-ph↗

arXiv2020

Appearance of objectivity for NV centers interacting with dynamically polarized nuclear environment

Quantum-to-classical transition still eludes a full understanding. Out of its multiple aspects, one has recently gained an increased attention - the appearance of objective world out of the quantum. One particularly idea is that objectivity appears thanks to specific quantum state structures formation during the evolution, known as Spectrum Broadcast Structures (SBS). Despite that quite some research was already performed on this strongest and most fundamental form of objectivity, its practical realization in a concrete physical medium has not been analyzed so far. In this work, we study the possibility to simulate objectivization process via SBS formation using widely studied Nitrogen-Vacancy centers in diamonds. Assuming achievable limits of dynamical polarization technique, we show that for high, but experimentally viable polarizations ($p>0.5$) of nuclear spins and for magnetic fields lower than $\approx \! 20$ Gauss the state of the NV center and its nearest polarized environment approaches reasonably well an SBS state.

quant-ph↗

arXiv2019

A glimpse of objectivity in bipartite systems for non-entangling pure dephasing evolutions

We study separable system-environment evolutions of pure dephasing type in the context of objectivity and find that it can lead to the natural emergence of Spectrum Broadcast Structure (SBS) states at discrete instances of time. Contrary to the standard way of obtaining SBS states which requires entanglement with the observed environment, reaching such states here does not require decoherence (no unobserved environements are necessary). Yet the biggest difference is the basis with respect to which the SBS states are formed. Here it is not the pointer basis of the system given by the interaction with the environment, but an equal superposition basis of said pointer states. The price to pay is the momentary character of the formed SBS structures, hence the term "glimpse".

quant-ph↗