Our visitor Dr. Shunji Matsuura from 1QBit, a startup company specializes in quantum computing and quantum information technology based in Vancouver, Canada gave a series of lectures from May 13 (Mon) through May 15 (Wed). Dr. Matsuura started with a basic explanation of qubits and their entanglement. Then, he moved on to explain various method employed in the field of quantum computing, such as Variational Quantum Eigensolver (VQE). His explanation was especially clear to physicists, since Dr. Matsuura’s background is string theory receiving his Ph.D. in string theory from the Perimeter Institute for Theoretical Physics and the University of Tokyo, and he used to conduct research at the Kavli Institute for Theoretical Physics (University of California, Santa Barbara), McGill University, Riken, YITP (Kyoto University), and the Niels Bohr Institute (University of Copenhagen). His current research focuses on the fundamental aspects of quantum-enhanced optimization, such as error correction and speedup, which are also of interest to some iTHEMS members, and we are hoping a lot of fruitful collaborations between iTHEMS and Dr. Matsuura as well as 1QBit group in future.

The first 15 min. coffee meeting talk in Reiwa era was given by Nagisa Hiroshima on May 10. She explained how to extract the density distribution of dark matter from observation.

A powerful mathematical method for simplifying the analysis of highly complex systems has been extended by a RIKEN-led team. This will enhance its usefulness for researchers in a wide range of fields.

AdS/CFT correspondence tells us that a gravity in AdS space is equivalent to CFT which lives on the boundary of the AdS. Recently it has been proposed that an integrable TT deformation of CFTs produces a deformed AdS/CFT. According to the conjecture, the AdS boundary is located at a finite radial cutoff. To investigate the deformed correspondence, we studied holographic entanglement entropy in the cutoff AdS, which is well known as a probe of information theoretic quantity. In particular, we explored its phase transitions. For two-interval entanglement entropy, the transition point monotonically decreases with a deformation parameter, which means that by the TT deformation the degrees of freedom in subsystems are decreasing. Our result implies that the effect of the TT deformation can be regarded as the rescaling of the energy scale.

My name is Kanato Goto and I have been working at iTHEMS since April 2019. I am a theoretical physicist studying string theory and my main research interests lie in foundational questions about quantum gravity, black hole physics, and supersymmetric quantum field theories. I am currently trying to understand the basic mechanism and the mysteries of the holographic principle, which states that information about gravity and the spacetime contained in our three-dimensional universe can be completely described by the two-dimensional boundary surrounding it, just like a hologram emerges from a sheet of photographic film. At iTHEMS, I hope to broaden my research horizon through discussions with researchers in various fields.