Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors.

Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using a cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp interfaces between BiSrCaCuO crystals, with quality approaching the limit set by intrinsic JJs. Near 45° twist angle, we observe fractional Shapiro steps and Fraunhofer patterns, consistent with the existence of two degenerate Josephson ground states related by time-reversal symmetry (TRS).

Revival Dynamics in a Traversable Wormhole.

Quantum effects can stabilize wormhole solutions in general relativity, allowing information and matter to be transported between two connected spacetimes. Here we study the revival dynamics of signals sent between two weakly coupled quantum chaotic systems, represented as identical Sachdev-Ye-Kitaev models, that realize holographically a traversable wormhole in anti-de Sitter spacetime AdS_{2} for large number N of particles. In this limit we find clear signatures of wormhole behavior: an excitation created in one system is quickly scrambled under its unitary dynamics, and is reassembled in the other system after a characteristic time consistent with holography predictions.

Detecting the Universal Fractional Entropy of Majorana Zero Modes.

A pair of Majorana zero modes (MZMs) constitutes a nonlocal qubit whose entropy is log2. Upon strongly coupling one of the constituent MZMs to a reservoir with a continuous density of states, a universal entropy change of 1/2log2 is expected to be observed across an intermediate temperature plateau. We adapt the entropy-measurement scheme that was the basis of a recent experiment by Hartman et al.

Fermi-Liquid Approach for Superconducting Kondo Problems.

We present a Fermi liquid approach to superconducting Kondo problems applicable when the Kondo temperature is large compared to the superconducting gap. To illustrate the theory, we study the current-phase relation and the Andreev level spectrum for an Anderson impurity between two s-wave superconductors. In the particle-hole symmetric Kondo limit, we find a 4π periodic Andreev spectrum.