Effective Particles in Quantum Spin Chains: The Framework

Laurens Vanderstraeten

Hugo Lóio, Jacopo De Nardis, Tony Jin

We develop a recently introduced representation of quantum dynamics based on sampling negative Markov chain processes. By introducing particles and antiparticles, this formalism maps generic quantum dynamics onto a Markov process defined over an exponentially large configuration space. Within this framework, quantum complexity arises from the proliferation of stochastic particles, which ultimately renders classical simulation and sampling intractable beyond a certain timescale. In the presence of noise, we demonstrate that for any unitary evolution generated by a linear combination of local or pairwise interactions, there exists at least one noise channel that effectively classicalizes the system by suppressing particle growth and making Monte Carlo sampling efficient. As a corollary, we show that for this class of unitaries, the dynamics of an open quantum spin chain subject to depolarizing noise undergoes an exact transition to classical simulability once the noise strength exceeds a critical threshold which can be efficiently determined for any model.

Jill C. Bonner, Henk W. J. Blöte, Hans Beck +1 more

A. Zheludev

Ning Sun, Lei Feng, Pengfei Zhang

The Efimov effect is a quantum phenomenon in which three particles form an infinite series of low-energy bound states at resonance, previously observed in three-dimensional systems. The authors extend this celebrated effect to long-range quantum spin systems, demonstrating long-range spin chains can also host Efimov states with widely tunable scaling ratios controlled by the interaction range.

Sudipto Singha Roy, Himadri Shekhar Dhar, Aditi Sen +1 more

We devise a method based on the tensor-network formalism to calculate genuine multisite entanglement in ground states of infinite spin chains containing spin-1/2 or spin-1 quantum particles. The ground state is obtained by employing an infinite time-evolving block decimation method acting upon an initial matrix product state for the infinite spin system. We explicitly show how such infinite matrix product states with translational invariance provide a natural framework to derive the generalized geometric measure, a computable measure of genuine multisite entanglement, in the thermodynamic limit of quantum many-body systems with both spin-1/2 and higher-spin particles.