QuCoLiMa Talk – Frank Pollmann – Entanglement Transitions in Unitary Circuit Games

Speaker:

Frank Pollmann - TU München

Title:

Entanglement Transitions in Unitary Circuit Games

Abstract:

Repeated projective measurements in unitary circuits can lead to an entanglement phase transition as the measurement rate is tuned. In this work, we consider a different setting in which the projective measurements are replaced by dynamically chosen unitary gates that minimize the entanglement. This can be seen as a one-dimensional unitary circuit game in which two players get to place unitary gates on randomly assigned bonds at different rates: The “entangler” applies a random local unitary gate with the aim of generating extensive (volume law) entanglement. The “disentangler”, based on limited knowledge about the state, chooses a unitary gate to reduce the entanglement entropy on the assigned bond with the goal of limiting to only finite (area law) entanglement. In order to elucidate the resulting entanglement dynamics, we consider three different scenarios: (i) a classical discrete height model, (ii) a Clifford circuit, and (iii) a general Haar random unitary circuit. We find that both the classical and Clifford circuit models exhibit phase transitions as a function of the rate that the disentangler places a gate, which have similar properties that can be understood through a connection to the stochastic Fredkin chain. In contrast, the “entangler” always wins when using Haar random unitary gates and we observe extensive, volume law entanglement for all non-zero rates of entangling.

Location:

Erlangen

All talks hybrid:

Mixture of on-site talks at the main sites of QuCoLiMa (Erlangen, Mainz, Saarbrücken) as well as online talks. Regardless of where the talks are given, they are livestreamed via Zoom and can be watched from home/office or cooperatively in the following meeting rooms:

- Erlangen: Livestream/Presentation in Lecture hall HF + open sandwiches in the foyer afterwards

- Saarbrücken: Livestream/Presentation in tba

- Mainz: Livestream/Presentation in tba

Zoom-Link:

http://www.qucolima.de/join-qucolima-talk

- - -

QuCoLiMa Talks are regular seminars of the collaborative research center TRR 306 QuCoLiMa (Quantum Cooperativity of Light and Matter), where (external) experts are invited to present their work.

More information at http://www.qucolima.de/talks