JQI

Abstract: Whether or not a physical system will thermalize from an initial state has been a key question in modern condensed matter physics. Closely related questions are determining whether observables in these systems relax to stationary values, and what those values are. Using tools from computational complexity theory, we demonstrate that given a Hamiltonian on a finite-sized system, determining whether or not it thermalizes or relaxes to a given stationary value is computationally intractable, even for a quantum computer.

Abstract: In [1] we constructed a family of two-dimensional topological stabilizer codes on continuous variable (CV) degrees of freedom, which generalize homological rotor codes and the toric-GKP code. Our topological codes are built using the concept of boson condensation -- we start from a parent stabilizer code based on an R gauge theory and condense various bosonic excitations.

Abstract: A set of universal fault-tolerant logical gates in quantum error correcting codes is necessary for quantum computing. Transversal operations applied independently on each qubit in a code block are naturally fault-tolerant and easy to implement, but the Eastin-Knill theorem states that the resulting discrete gate set cannot be universal. Circumventing this requires complex protocols such as magic state distillation, code switching, etc. Surface code error correction has been demonstrated on several experimental platforms.

Abstract: One approach to ion-photon entanglement relies on transitions from 2P3/2 to the low-lying 2D3/2 and 2D5/2 states at 1345 nm and 1650 nm in Yb+ [1]. Here Purcell enhancement is crucial for achieving good performance in the context of quantum networking. In support of this effort, we developed a monolithic, fiber-coupled Fabry–Pérot cavity integrated with a blade trap that operates at cryogenic temperatures. One of the cavity mirrors is bonded to a metalens that mode-matches cavity light to a single-mode fiber.