Seminar

Correlations and entanglement in quantum many-body systems: detection, computation and applications

Speaker: Roopayan Ghosh (Dept. of Physics and Astronomy, University College London, United Kingdom)

Date and time
Venue
SCM Lecture hall

Abstract

In this talk, I will explore various aspects of quantum correlations and quantum entanglement within the context of quantum many-body systems.

In the first part of my presentation, I will address the challenges associated with detecting and measuring entanglement in generic quantum many-body states, particularly in mixed states. I will then demonstrate how, under specific conditions, these challenges can be significantly simplified

[1]. Following this, I will discuss how quantum entanglement might be used to quantify quantum causality through a quantity known as quantum Liang information, which offers a natural extension of classical ideas

[2].In the second part, I will delve into the computation of well-known entanglement measures, such as entanglement entropy and negativity, for quantum many-body systems. I will focus on the simplifications that can be achieved for Gaussian systems, which allow for the study of exact entanglement dynamics in large systems governed by quadratic Hamiltonians. I will also discuss an intriguing phenomenon that emerges using this method

[3]. Additionally, I will briefly describe the generalization of this technique to quadratic action, using the Mott insulator-superfluid transition in the Bose-Hubbard model as an example

[4].In the final part of my talk, I will discuss how the application of concepts from quantum entanglement can enhance our understanding of quantum many-body systems. I will begin by discussing many-body localized (MBL) systems, where a quantity known as number entropy has sparked debate in the community regarding the validity of the MBL phase due to observations of its slow increase. I will explain the reasons behind this slow increase and demonstrate how it can be accounted for within the framework of MBL[5]. Next, I will explore open localized systems and resolve a longstanding debate concerning the relaxation of imbalance with the addition of dephasing, using a range of analytical and numerical tools[6]. Finally, I will conclude by illustrating how quantum entanglement presents a fundamental bottleneck in adiabatic quantum annealing and discuss a recent proposal we have presented to mitigate this effect.[7,8]

References:-

  1. R Ghosh, S Bose, Physical Review Research 6 (2), 023132.
  2. R Ghosh, B Yi, S Bose, arXiv preprint arXiv:2403.19364.
  3. R Ghosh, A Das, Physical Review B 103 (2), 024202.
  4. R Ghosh, N Dupuis, A Sen, K Sengupta, Physical Review B 101 (24), 245130.
  5. R Ghosh, M Žnidarič, Physical Review B 105 (14), 144203.
  6. R Ghosh, M Žnidarič, Physical Review B 107 (18), 184303.
  7. R Ghosh, LA Nutricati, PA Warburton, N Feinstein and S Bose, in preparation.

LA Nutricati, R Ghosh, PA Warburton, N Feinstein and S Bose, in preparation