Nonuniversal entanglement level statistics in projection-driven quantum circuits

Speaker: Lei Zhang, Boston University, Physics Department

When: March 20, 2020 (Fri), 10:00AM to 11:00AM (add to my calendar)

This event is part of the Departmental Seminars.

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.

Dissertation Committee: A. E. Ruckenstein, C. Chamon, M. El-Batanouny, R. Brower (ECE)

Link of Zoom Seminar Event: