The dynamics of systems consisting of many particles are very complicated and practically impossible to predict. For such systems, statistical physics has proven extremely useful, making highly accurate predictions for both quantum and classical systems. The central assumption behind statistical physics is the maximum entropy principle: A generic system reaches a state with maximum entropy,...

Many-body quantum systems reach thermal equilibrium due to a property called quantum ergodicity. Despite its conceptual significance, there is no general definition of quantum ergodicity that is universally applicable to all scenarios. In quantum systems whose description remains unchanged with time, quantum ergodicity is defined through the system’s stationary configurations — certain states that do not...

The U.S. National Science Foundation’s Physics Frontiers Centers program renewed a grant to the MIT-Harvard Center for Ultracold Atoms (CUA) to fund exploring, understanding, and harnessing mysterious phenomena at the frontiers of physics. The CUA, which works to enable greater control and programmability of quantum-entangled systems of low-temperature atoms and molecules, will conduct experiments involving...

Quantum simulators—carefully engineered and programmable quantum systems—provide an exciting avenue to explore the laws of nature and to realize complex physical phenomena. However, current quantum simulators still lack the sophisticated controls needed to interrogate a prepared state in depth, limiting the information that can be extracted by measurements. Here, we propose a novel measurement protocol...

We have developed a new method to quantify the performance of analog quantum simulators, using insights from quantum chaos.  The state fidelity quantifies the closeness of two quantum states. While theoretically simple, the fidelity is difficult to measure in experiments since most conventional approaches require sophisticated controls not accessible in existing devices. CUA researchers and...

With rapid advances in our experimental capability to perform quantum simulations, it is also important to ask what interesting physical phenomena we would like to explore. One interesting direction is the realization of deconfined quantum criticality (DQC), a concept central to the modern understanding of various quantum phase transitions yet experimentally unobserved phenomena. In conventional...