The simulation of correlated real materials remains one of the big challenges of solid state physics, in particular due to the fact that the physical behaviour is often determined by energy scales which are extremely small compared to the raw scales of the substances. In this talk I will discuss how extending time evolution into the complex plane alleviates entanglement issues to an extent...
Information-theoretic quantities, such as Rényi entropies, exhibit remarkable universality in their late-time behavior across a wide range of chaotic quantum many-body systems. Understanding how these common features arise from vastly different microscopic dynamics remains an important challenge. In this talk, I will show this mechanism for a class of one-dimensional Brownian models with...
I will report on work, both published and unpublished, on constrained East type models.
Starting from a pure initial state, the local properties of chaotic many-body quantum systems are expected to quickly thermalize under unitary dynamics. The remaining evolution from local to global equilibrium is described by the classical equations of hydrodynamics. However, the advent of quantum simulator platforms has made it possible to measure not only local expectation values, but also...
We prove an analogue of the “bottleneck theorem”, well-known for classical Markov chains, for Markovian quantum channels. In particular, we show that if two regions (subspaces) of Hilbert space are separated by a region that has very low weight in the channel’s steady state, then states initialized on one side of this barrier will be stuck for a long time. This puts a lower bound on the mixing...
In recent years, superconducting qubits have emerged as a leading platform for quantum simulation, particularly for studying quantum dynamics on Noisy Intermediate-Scale Quantum (NISQ) processors. I will discuss some of our work within this broad area of research. In a recent study [1], we directly image the dynamics of charges and strings in (2+1)-dimensional lattice gauge theories. We...
Quantum simulation is a promising route to studying nonequilibrium physics of strongly-coupled quantum systems, including gauge theories of relevance to nuclear and high-energy physics. We develop a quantum-thermodynamic framework to study lattice gauge theories in and out of equilibrium, focusing on protocols which can be implemented in quantum simulations, and finding thermodynamic...
In this talk, I will discuss how ultra cold atoms in Raman optical lattices can serve as quantum simulators of Gross-Neveu QFTs. I will describe our recent studies related to particle production and entanglement dynamics in analogue expanding spacetimes, and how finite-density crystalline phases related to inhomogeneous chiral condensates could be accessed by varying the atomic filling.
Ordinarily we think that at high enough temperatures, systems become disordered and are in a thermodynamically trivial phase. For classical and quantum lattice models of interacting spins, theorems indeed prove that there is no long-range order or entanglement above a sufficiently high temperature. I will show how it is nevertheless possible to engineer models that order at arbitrarily...
In the study of out-of-equilibrium many-body quantum systems, growing attention has been given to understanding how symmetries evolve over time under unitary dynamics. Key questions include whether symmetries are dynamically restored in local subsystems and how the timescales involved depend on the initial states and the dynamics of the system. In this talk, we introduce the entanglement...
Adaptive quantum circuits—where a quantum many-body state is controlled using measurements and conditional unitary operations—are a powerful paradigm for state preparation and quantum error-correction tasks. They can support two types of nonequilibrium quantum phase transitions: measurement-induced transitions between volume- and area-law-entangled steady states and control-induced transitions...
We highlight two key experimental breakthroughs achieved using the QCCD trapped-ion Quantinuum Systems. First, by simulating digitized dynamics of the quantum Ising model, we observed Floquet prethermalization and local equilibration at circuit volumes exceeding 2000 gates, beyond classical simulation capabilities. Second, leveraging a randomized quantum algorithm, we successfully simulated...
I will provide a framework for computing time-averaged dynamics in locally interacting systems in any dimension. It is based on pseudolocal dynamical symmetries generalising pseudolocal charges and unifies seemingly disparate manifestations of quantum non-ergodic dynamics including quantum many-body scars, continuous, discrete and dissipative time crystals, Hilbert space fragmentation, lattice...
The original PXP chain that opened experimentally the field of quantum many-body scars continues to surprise us. I will first describe discovery [1] of exact volume-entangled eigenstates in this and many related models (including in higher dimensions). I will then describe finding [2] of several new exact scars with finite bond dimension in the PXP chain, including some that provide an...
Dynamics driven by quantum fluctuations are important for the formation of exotic quantum phases of matter, fundamental high-energy processes, quantum metrology, and quantum algorithms. In this talk, I will the describe our use of a programmable quantum simulator based on Rydberg atom arrays to experimentally study collective dynamics across a (2+1)D Ising quantum phase transition. After...
Reconfigurable arrays of neutral atoms have emerged as a leading platform for quantum science. Their excellent coherence properties combined with programmable Rydberg interactions have led to intriguing observations such as quantum phase transitions, the discovery of quantum many-body scars, and novel quantum computing architectures.
Here, I am introducing a dual-species Rydberg array that...
Thermalization is deeply connected to the notion of ergodicity in Hilbert space, implying the equipartition of the wave function over the available many-body Fock states. Under unitary time evolution, an initially structured state spreads in Fock space, approaching a Haar-random state, thereby revealing a deep connection between many-body quantum systems and random matrix theory.
In the first...
I will describe a mixed quantum-classical framework, dubbed the Moving Born-Oppenheimer Approximation (MBOA), to describe the dynamics of slow degrees of freedom coupled to fast ones. The key assumption is that the fast degrees of freedom adiabatically follow a state that depends on the position and momenta of the slow degrees of freedom. The MBOA reveals rich dynamics; for example, the fast...
In this talk, I will present our recent studies of quantum magnetism using a Rydberg quantum simulator. I will first explain how, using two different Rydberg levels such as nS and nP, we can study the equilibrium properties and the dynamics of dipolar XY magnets, in one [1] and two dimensions [2,3]. I will then show that by using three Rydberg states, nS, nP, and n’S, one can realize a bosonic...
In this talk, I will present a proof of delocalization in spin chains symmetric under a combination of mirror and spin-flip symmetries and with a nondegenerate spectrum. The proof applies to two prominent examples: the Stark many-body localization system (Stark-MBL) and the symmetrized many-body localization system (symmetrized–MBL). I will also provide numerical evidence of delocalization at...
Persistent revivals recently observed in Rydberg atom arrays have challenged our understanding of thermalisation and attracted much interest to the concept of quantum many-body scarring : the presence of coherent dynamics in otherwise chaotic Hamiltonians. They have since been reported in multiple models, including the kinetically-constrained PXP model realised in Rydberg chains. At the same...
Neutral-atom qubits offer a promising platform for fault-tolerant quantum computing. We demonstrate a quantum computer—featuring 100s of atomic qubits, a universal gateset, and qubit movement—performing error correction and computation on 24-28 logical qubits.
Understanding the out-of-equilibrium dynamics of a closed quantum system driven across a quantum phase transition is an important problem with widespread implications for quantum state preparation and adiabatic algorithms. While the quantum Kibble-Zurek mechanism elucidates part of these dynamics, the subsequent and significant coarsening processes lie beyond its scope. Here, we develop a...
