## Nonuniversal entanglement level statistics in projection-driven quantum circuits

**Note:**https://bostonu.zoom.us/j/96327880887?pwd=ajFhL0xtc

**Speaker:**Lei Zhang, Boston University, Physics Department

**When:**November 30, 2020 (Mon), 09:00AM to 10:00AM (add to my calendar)

*This event is part of the PhD Final Oral Exams. *

We study the level-spacing statistics in the entanglement spectrum of output states of random universal quantum circuits where qubits are subject to a finite probability of projection to the computational basis at each time step. We encounter two phase transitions with increasing projection rate: The first is the volume-to-area law transition observed in quantum circuits with projective measurements; The second separates the pure Poisson level statistics phase at large projective measurement rates from a regime of residual level repulsion in the entanglement spectrum within the area-law phase, characterized by non-universal level spacing statistics that interpolates between the Wigner-Dyson and Poisson distributions. By applying a tensor network contraction algorithm to the circuit spacetime, we identify this second projective-measurement-driven transition as a percolation transition of entangled bonds. The same behavior is observed in both circuits of random two-qubit unitaries and circuits of universal gate sets, including the set implemented by Google in its Sycamore circuits.

ZOOM LINK https://bostonu.zoom.us/j/96327880887?pwd=ajFhL0xtc Meeting ID: 963 2788 0887 Passcode: 623254