Speaker: Takaaki Minato (Keio University)

Date & Time: 3pm, Jun. 17, 2021.

Title: Fate of measurement-induced phase transition in long-range interaction

Abstract: In general, the entanglement entropy of isolated quantum system grows in time and eventually reaches the order of system size (volume-law of the entanglement entropy). Conversely, it is also known that sufficient strong local quantum measurements completely suppress the entanglement growth and the quantum state is completely frozen at zero entangled state, i.e., the quantum Zeno effect. The quantum Zeno effect is an extreme case of the area-law of the entanglement entropy. Recently, it has been discovered that as gradually increasing the amplitude of measurement, the entanglement of the system shows a phase transition at a finite amplitude of measurement from the (sub)-volume law to the area law phase. This phenomenon is now called the measurement-induced phase transition (MIP). So far, the MIP has been intensively studied using quantum circuit models as well as Hamiltonian-based models with nearest-neighbor interactions. [1-3].

On the other hand, it is known from various equilibrium phase transitions in the statistical physics that long-range interactions qualitatively affect the equilibrium phases. Hence, it is also fundamental to figure out effect of long-range interaction in the MIP. To address this problem, we introduce toy quantum models, which are integrable and nonintegrable fermion systems with long-range interactions that decays as 1/ r^alpha with distance r. We first numerically investigate how the exponent alpha affects the MIP. We next analytically consider a sufficient condition for a general d-dimensional systems to show the MIP. In this seminar, I present our findings on these. My talk is based on a joint work with K. Sugimoto, T. Kuwahara, and K. Saito [4].

[1] Li, Chen, Fisher, PRB , vol.98, 205136 (2018)

[2] Skinner, Ruhman, Nahum, PRX, vol.9, 031009 (2019)

[3] Alberton, Buchhold, Diehl, PRL, vol.126, 170602 (2021)

[4] Minato, Sugimoto, Kuwahara, Saito, arxiv:2104.09118 [quant-ph] (2021)