Real-time dynamics of string breaking in quantum spin chains

Abstract

String breaking is a central dynamical process in theories featuring confinement, where a string connecting two charges decays at the expense of the creation of new particle-antiparticle pairs. Here, we show that this process can also be observed in quantum Ising chains where domain walls get confined either by a symmetry-breaking field or by long-range interactions. We find that string breaking occurs, in general, as a two-stage process. First, the initial charges remain essentially static and stable. The connecting string, however, can become a dynamical object. We develop an effective description of this motion, which we find is strongly constrained. In the second stage, which can be severely delayed due to these dynamical constraints, the string finally breaks. We observe that the associated timescale can depend crucially on the initial separation between domain walls and can grow by orders of magnitude by changing the distance by just a few lattice sites. We discuss how our results generalize to one-dimensional confining gauge theories and how they can be made accessible in quantum simulator experiments such as Rydberg atoms or trapped ions.

Designing nonequilibrium states of quantum matter through stochastic resetting

“…The unitary dynamics from the reset state |j (j = 1, 2), |ψ j (τ ) = exp(−iHτ ) |j (setting = 1), between consecutive resets stems therefore from a quench of the transverse field from the pre-quench h 0 = 0 to the post-quench value h [46][47][48][49][50][51][52][53][55][56][57][58][59][60][61][62][63]. The experimental motivation behind the conditional reset protocol comes from recent results on Rydberg quantum simulators [64], which allow to experimentally implement Ising models with transverse and longitudinal fields [65][66][67][68][69][70][71][72] and permit, at the same time, the spatially resolved detection of the spin state upon which the reset is conditioned. Such measurement has been indeed implemented in Rydberg atoms experiments on quantum quenches of the Ising model [73][74][75][76].…”

Fragmentation and emergent integrable transport in the weakly tilted Ising chain

“…In the ferromagnetic case, this immediately leads to confinement of fermionic domain walls into bosonic magnons [6][7][8][9]. Recent studies of the Ising chain in a tilted field concentrated on aspects of anomalously slow dynamics [10][11][12][13][14], quantum scarring [15,16], prethermalization [17], fractons [18], meson scattering [19,20] and dynamics of the false vacuum [21][22][23][24][25][26].…”

Fractionalized holes in one-dimensional $\mathbb{Z}_2$ gauge theory coupled to fermion matter -- deconfined dynamics and emergent integrability

“…Introduction -Identifying the origin of a linear attractive potential between charges mediated by gauge fields, known as confinement, and studying its consequences has been a longstanding challenge in nuclear, high-energy and condensedmatter physics [1][2][3][4]. Recently, consequences of confinement on real-time quantum dynamics in spin chains and equivalent lattice gauge theories have been studied extensively [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Generically, confinement is known to hinder quantum thermalization and slow quantum dynamics by strongly suppressing the spreading of quantum correlations and entanglement growth.…”

“…a state fully filled with fermions. In order to follow the time evolution of this state, one needs to solve the time-dependent Schrödinger equation, which for this case reads [47] i∂ T ψ m = −t(ψ m+1 + ψ m−1 ) + h(1 + (−1) m+1 )ψ m (7) revealing an effective zig-zag potential (albeit with the opposite sign as compared to Fig. 1).…”