We study the entanglement entropy of quantum trajectories a free fermion chain under continuous monitoring local occupation numbers. propose simple theory for evolution from disentangled and highly excited initial states. It is based on generalized hydrodynamics quasi-particle pair approach to in integrable systems. test several quantitative predictions against extensive numerics find good agreement. In particular, volume law destroyed by presence arbitrarily weak measurement.

The possibility that a classical space-time and quantum matter cohabit at the deepest level, i.e. of having fundamental not phenomenological semiclassical gravity, is often disregarded for lack good candidate theory. standard theory suffers from inconsistencies (e.g.: Schr\"odinger cat sources, faster-than-light communication violation Born rule) which can only be ignored in simple typical situations. We harness power spontaneous localization models, historically constructed to solve...

We introduce a new class of states for bosonic quantum fields which extend tensor network to the continuum and generalize continuous matrix product (cMPS) spatial dimensions $d\geq 2$. By construction, they are Euclidean invariant, genuine limits discrete states. Admitting both functional integral an operator representation, share important properties their counterparts: expressiveness, invariance under gauge transformations, simple rescaling flow, compact expressions $N$-point functions...

Recent works have proved that semi-classical theories of gravity needed not be fundamentally inconsistent, at least in the Newtonian regime. Using machinery continuous measurement theory and feedback, it was shown one could construct well behaved models hybrid quantum-classical dynamics price an imposed (non unique) decoherence structure. We introduce a principle (PLD) which allows to naturally single out unique model from all available options; up some unspecified short distance...

This note derives the stochastic differential equations and partial equation of general hybrid quantum–classical dynamics from theory continuous measurement (non-Markovian) feedback. The advantage this approach is an explicit parameterization, without additional positivity constraints. construction also neatly separates different effects: how quantum influences classical quantum. modular presentation gives a better intuition what to expect dynamics, especially when used construct possibly...

Small quantum systems can now be continuously monitored experimentally which allows for the reconstruction of trajectories. A peculiar feature these trajectories is emergence jumps between eigenstates observable measured. Using Stochastic Master Equation (SME) formalism continuous measurements, we show that density matrix a system indeed shows jumpy behavior when it subjected to tight measurement (even if noise in SME Gaussian). We are able compute jump rates analytically any evolution, i.e....

A quantum system subjected to a strong continuous monitoring undergoes jumps. This very-well-known fact hides neglected subtlety: sharp scale-invariant fluctuations invariably decorate the jump process, even in limit where measurement rate is very large. article devoted quantitative study of these remaining fluctuations, which we call spikes, and discussion their physical status. We start by introducing classical model origin more intuitive, then realm existence less intuitive. compute exact...

Spontaneous wave-function collapse models, like continuous spontaneous localization, are designed to suppress macroscopic superpositions while preserving microscopic quantum phenomena. An observable consequence of models is heating massive objects. We calculate the collapse-induced rate astrophysical objects, and corresponding equilibrium temperature. apply these results neutron stars, densest phase baryonic matter in Universe. Stronger model parameters imply greater heating, allowing us...

We propose a method to compute expectation values in 1+1-dimensional massive Quantum Field Theories (QFTs) with line defects using Relativistic Continuous Matrix Product State (RCMPS). Exploiting Euclidean invariance, we use quantization scheme where (imaginary) time runs perpendicularly the defect. With this choice, correlation functions of local operators presence defect can be computed as extended no-defect vacuum, which approximated by homogeneous RCMPS. demonstrate effectiveness...

A bstract We propose a method to compute expectation values in 1+1-dimensional massive Quantum Field Theories (QFTs) with line defects using Relativistic Continuous Matrix Product State (RCMPS). Exploiting Euclidean invariance, we use quantization scheme where (imaginary) time runs perpendicularly the defect. With this choice, correlation functions of local operators presence defect can be computed as extended no-defect vacuum, which approximated by homogeneous RCMPS. demonstrate...

Using quantum parallelism on random walks as the original seed, we introduce new stochastic processes, open Brownian motions. They describe behaviors of walkers—with internal degrees freedom which serve gyroscopes—interacting with a series probes coins. These processes may also be viewed scaling limit and develop this approach along three different lines: trajectory, dynamical map differential equation. We present study simplest case, two level system an gyroscope, illustrating interplay...

This paper presents a method to write the partition function of ${\ensuremath{\phi}}^{4}$ theory as tensor network and obtain its renormalization group flow map in space tensors. The authors also compute critical coupling constant ${f}_{\mathrm{c}}=\ensuremath{\lambda}/{\ensuremath{\mu}}^{2}$ continuum find ${f}_{\mathrm{c}}^{\mathrm{cont}.}=11.0861(90)$ compare with other methods.

Open quantum random walks (OQRWs) deal with motions on a line for systems internal and orbital degrees of freedom. The system behaves as gyroscope coding the direction moves. We reveal existence transition, depending OQRW moduli, in behaviors from simple oscillations to flips between two unstable pure states. This induces transition usual diffusion ballistically induced large mean free path effective constant at times. also show that mixed states are converted into during process. touch upon...

It is well known that during homology recognition and strand exchange the double stranded DNA (dsDNA) in DNA/RecA filaments highly extended, but functional role of extension has been unclear. We present an analytical model calculates distribution tension extended dsDNA exchange. The suggests binding additional base pairs to filament alters was already bound filament, resulting a non-linear increase mechanical energy as function number pairs. This collective response may promote stringency...

Inspired by RecA-protein-based homology recognition, we consider the pairing of two long linear arrays binding sites. We propose a fully reversible, physically realizable biased random walk model for rapid and accurate self-assembly due to spontaneous matching sites, where statistics searched sample are included. In model, there bound conformations, free energy each conformation is weakly nonlinear function number contiguous matched

This Rapid Communication provides an exact formula for the signal $n$-point correlation functions of detectors continuously measuring arbitrary quantum system, in presence detection imperfections. The derivation uses only continuous stochastic calculus techniques, but final result is easily understood from a discrete picture repeated interactions with qubits or parallel matrix product states. crude yet efficient way to estimate system parameters directly experimental data, without requiring...

I introduce a modification of the Ghirardi-Rimini-Weber (GRW) model in which flashes (or space-time collapse events) source classical gravitational field. The resulting semiclassical theory Newtonian gravity preserves statistical interpretation quantum states matter contrast with mean field approaches. It can be seen as discrete version recent proposals consistent hybrid theories. is agreement known experimental data and introduces new falsifiable predictions: (1) single particles do not...

Abstract It is often argued that gravity has to be a quantum theory simply because fundamentally semiclassical approach would necessarily inconsistent. Here I review recent Newtonian toy models of (stochastic) gravity. They provide one option implement force semiclassically without getting into the known problems associated with mean-field. These are not complete theories and should considered too seriously, but their consistency shows hard dismiss on purely theoretical grounds.

We propose to use the effect of measurements instead their number study time evolution quantum systems under monitoring. This redefinition acts like a microscope which blows up inner details seemingly instantaneous transitions jumps. In simple example continuously monitored qubit coupled heat bath, we show that this procedure provides well defined and equations in an otherwise singular strong monitoring limit. there exists anomalous observable localised on sharp can only be resolved with our...

I introduce a modification of continuous matrix product states (CMPS) that makes them adapted to relativistic quantum field theories (QFT). These CMPS can be used solve genuine 1+1 dimensional QFT without UV cutoff and directly in the thermodynamic limit. The main idea is work basis diagonalizes free part model considered, which allows fit its short distance behavior exactly. This computations slightly less trivial than with standard CMPS. However, they remain feasible present all steps...

We propose a self-contained and accessible derivation of an exact formula for the n-point correlation functions signal measured when continuously observing quantum system. The expression depends on initial state Stochastic Master Equation (SME) governing dynamics. This applies to both jump diffusive evolutions takes into account common imperfections realistic measurement devices. show how these correlations can be efficiently computed numerically commonly filtered integrated signals...

We propose a reformulation of quantum field theory (QFT) as relativistic statistical theory. This rewriting embeds collapse model within an interacting QFT and thus provides possible solution to the measurement problem. Additionally, it relaxes structural constraints on standard QFTs hence might open way future mathematically rigorous constructions well new numerical methods. Finally, because shows that models can be hidden QFTs, this article calls for reconsideration dynamical program,...

The variational method is a powerful approach to solve many-body quantum problems nonperturbatively. However, in the context of relativistic field theory, it needs meet three seemingly incompatible requirements outlined by Feynman: extensivity, computability, and lack UV sensitivity. In practice, methods break one three, which translates into need have an IR or cutoff. this letter, I introduce modification continuous matrix product states that satisfies jointly $1+1$ dimensions. apply...

Understanding the emergence of a tangible 4-dimensional space-time from quantum theory gravity promises to be tremendously difficult task. This article makes case that this task may not have carried. Space-time as we know it fundamental begin with. I recall common arguments against possibility and review class recently discovered models bypassing most serious objection. The generic solution measurement problem is tied semiclassical well difficulty alternative make reasonable default option...

We define a time continuous version of the concept "local operations and classical communication" (LOCC), ubiquitous in quantum information theory. It allows us to construct GKLS master equations for particle systems that have (1) an arbitrary pair potential, (2) local decoherence terms, but do not entangle constituents. The terms take particularly simple form if principle least is applied.