Abstract Weak values and Kirkwood–Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory advantages metrology. We propose simple circuits to measure weak values, KD distributions, spectra of density matrices without the need for post-selection. This is achieved by measuring unitary-invariant, relational properties states, which are functions Bargmann invariants, concept that underpins our unified perspective. Our also...

We analyse nonclassical resources in interference phenomena using generalized noncontextuality inequalities and basis-independent coherence witnesses. use recently proposed that witness both within the same framework. also propose, view of previous contextual advantage results, a systematic way applying these tools to characterize provided by contextuality quantum information protocols. instantiate this methodology for task interrogation, famously introduced paradigmatic bomb-testing...

Quantum theory is traditionally formulated using complex numbers. This imaginarity of quantum has been quantified as a resource with applications in discrimination tasks, pseudorandomness generation, and metrology. In the standard formulation, state said to have "imaginarity" if associated density matrix not real-valued given, fixed basis. If instead we consider set states, it possible devise tests that guarantee some set, independently basis chosen. Here propose such basis-independent...

Quantum superposition of high-dimensional states enables both computational speed-up and security in cryptographic protocols. However, the exponential complexity tomographic processes makes certification these properties a challenging task. In this work, we experimentally certify coherence witnesses tailored for quantum systems increasing dimension using pairwise overlap measurements enabled by six-mode universal photonic processor fabricated with femtosecond laser writing technology....

The significance of anomalous weak values has been a matter great debate in quantum foundations and information. Here, simple proof shows that the weak-value anomaly requires both negativity certain quasiprobability representation coherence pre- postselected states observable's basis.

Quantum coherence, nonlocality, and contextuality are key resources for quantum advantage in metrology, communication, computation. We introduce a graph-based approach to derive classicality inequalities that bound local, noncontextual, coherence-free models, offering unified description of these seemingly disparate resources. Our generalizes recently proposed basis-independent coherence witnesses, it recovers all noncontextuality the exclusivity graph approach. Moreover, violations certain...

Quantum Darwinism proposes that the proliferation of redundant information plays a major role in emergence objectivity out quantum world. Is this kind necessarily classical? We show if one takes Spekkens' notion noncontextuality as classicality and approach Brand\~{a}o, Piani Horodecki to Darwinism, answer above question is `yes', environment encodes sufficiently well proliferated information. Moreover, we propose threshold on encoding, which can unambiguously say classical has emerged under...

Kirkwood-Dirac representations of quantum states are increasingly finding use in many areas within theory. Usually, this sort only applied to provide a representation (as complex functions over some set). We show how standard can be extended fully compositional all theory (including channels, measurements, and so on), prove that extension satisfies the essential features functoriality (namely, commutes with composition channels), linearity, quasistochasticity. Interestingly, positive...

An alternative approach to the usual perturbative S-matrix evaluation of quantum field theories is presented which nonperturbative and provides full space-time resolution. We study dynamical development force between two fermion wave packets for Yukawa system. The spatial distribution virtual bosons that act as mediators can be analyzed along with fermionic densities. Using a potential function fermion-fermion interaction good approximation theoretical calculations when Fock space restricted...

Weak values and Kirkwood--Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory advantages metrology. We propose simple circuits to measure weak values, KD distributions, spectra of density matrices without the need for post-selection. This is achieved by measuring unitary-invariant, relational properties states, which are functions Bargmann invariants, concept that underpins our unified perspective. Our also enable...

The standard Klein paradox describes how an incoming electron scatters off a supercritical electrostatic barrier that is so strong it can generate electron-positron pairs. This fermionic system has been widely discussed in textbooks to illustrate some of the discrepancies between quantum mechanical and field theoretical descriptions for pair creation process. We compare dynamics with corresponding bosonic system. point out direct counterpart Pauli exclusion principle (the central mechanism...

We analyse nonclassical resources in interference phenomena using generalized noncontextuality inequalities and basis-independent coherence witnesses. use recently proposed that witness both within the same framework. also propose, view of previous contextual advantage results, a systematic way applying these tools to characterize provided by contextuality quantum information protocols. instantiate this methodology for task interrogation, famously introduced paradigmatic bomb-testing...

We propose a mechanism for experimental investigation of relativistic effects in the laser-atom interaction with moderate (nonrelativistic) laser intensities that involves placing system static magnetic field parallel to laser's magnetic-field component. The resonantly induced motion atomic electron leads variety novel phenomena: dephasing leading ringlike spatial probability density, counterintuitive window relativistically enhanced motion, and sequence sawtooth-shaped resonances may...

Using numerical solutions to quantum field theory, the creation of boson-antiboson pairs from vacuum under a very strong localized external electric is explored. The simulations reveal that initial linear increase number particles turns into an exponential growth. This self-amplification can be understood as result interaction previously generated with process. While keeps increasing, spatial shape (normalized) charge density created reaches universal form related bound states supercritical...

Abstract We employ the resource theory of generalized contextuality as a tool for analyzing structure prepare-and-measure scenarios. argue that this framework simplifies proofs quantum in complex scenarios and strengthens existing arguments regarding robustness experimental implementations. As case study, we demonstrate associated with any nontrivial noncontextuality inequality class useful by noticing connection between measurement simulability. Additionally, expose formal composition rule...

We compare the relativistic time evolution of an initially localized quantum particle obtained from Schr\"odinger, Klein-Gordon and Dirac equations. By computing amount spatial probability density that evolves outside light cone we quantify causality violation for Schr\"odinger Hamiltonian. comment on relationship between field theoretical transition amplitudes, commutators fields their bilinear combinations as indicators a possible violation. point out relevance localization problem to this...

We analyze the interaction of fermions and bosons through a one-dimensional Yukawa model. numerically compute energy eigenstates that represent physical fermion, which is superposition bare fermionic bosonic uncoupled Hamiltonian. It turns out even fast require only low-momentum dressing bosons, attach themselves to fermion quantum correlations. compare space-time evolution with its counterpart show importance using dressed observables. The time center mass as well wave packet's spatial...

We study the scattering of a boson with fermion full spatial and temporal resolution based on one-dimensional Yukawa Hamiltonian. In quantum field theory this interaction is described by annihilation creation bosons intermediate virtual particle states. show that process can be modeled in center-of-mass frame potential, permitting us to interpret absorption re-emission processes mechanical terms characteristic force. This Compton force between repulsive for large distances attractive shorter...

We propose an alternative technique for numerically renormalizing quantum field theories based on their Hamiltonian formulation. This method is nonperturbative in nature and, therefore, exact to all orders. It does not require any correlation functions or Feynman diagrams. illustrate this a model Yukawa-like theory describing the interaction of electrons and positrons with photons one spatial dimension. show that, after mass renormalization fermionic bosonic single-particle states, other...

Quantum coherence, nonlocality, and contextuality are key resources for quantum advantage in metrology, communication, computation. We introduce a graph-based approach to derive classicality inequalities that bound local, non-contextual, coherence-free models, offering unified description of these seemingly disparate resources. Our generalizes recently proposed basis-independent coherence witnesses, recovers all non-contextuality the exclusivity graph approach. Moreover, violations certain...

We study the generation of high-order harmonics during ionization process for atoms described by relativistic classical mechanics with a special focus on retardation and Doppler shifts. will then extend discussion to regime which atom-laser interaction takes place in static homogeneous magnetic field. demonstrate theoretically possibility tune strength field resonances enhance frequency components scattered light harmonic signal.

Using a simplistic model in one spatial dimension, we estimate the impact of electron-electron, positron-positron, and electron-positron forces on yield pair-creation process triggered by an external superstrong force. We separate scalar vector potentials Dirac equation into internal parts, where dynamics are governed Maxwell equations with charge current densities as source terms. In order to explore interfermionic forces, compute number created pairs, time evolution charge, density well...

Abstract Recently, cat states have been used to heuristically improve the runtime of a classical simulator quantum circuits based on diagrammatic ZX-calculus. Here we investigate use cat-state injection within circuit model. We explore family states, $\left| \mathrm{cat}_m^* \right>$, and describe gadgets using them concurrently inject non-stabilizerness (also known as magic) entanglement into any circuit. provide numerical evidence that does not lead speed-up in simulation. On other...

The time-dependent Dirac equation is solved numerically on a space-time grid for an atom in strong static magnetic field and laser field. resonantly induced relativistic motion of the atomic electron leads to ringlike spatial probability density similar features that have been recently predicted [Wagner, Su, Grobe, Phys. Rev. Lett. 84, 3282 (2000)] based phase-space method. We further demonstrate spin-orbit coupling fast-moving such becomes significant time dependence spin can dephase even...

We compare the time evolution of quantum-mechanical spatial probability density obtained by solving time-dependent Dirac equation with its classical counterpart from relativistic Liouville for phase-space in a regime which dynamics is essentially relativistic. For resonantly driven one-dimensional harmonic oscillator, simplest nontrivial model system to perform this comparison, we find that, despite nonlinearity induced relativity, ensemble description matches quantum remarkably well.