Quantum computers (QC) are the only known technology to have possible performance exponentially faster than the classical computers. Due to the rapid technological advances in recent years, the number of qubits in digital QC (analogue QC) is now approaching ~100 (~2000).  They are still noisy devices, however, but we are now entering the era of noisy intermediate-scale quantum (NISQ) computers.

Although it is hard to predict when practically important problems can be solved with full-fledged fault-tolerant QC,  “quantum computing is valuable for driving foundational research that will help advance humanity’s understanding of the universe. As with all foundational scientific research, discoveries from this field could lead to transformative new knowledge and applications” as emphasized in the recent report, Quantum Computing: Progress and Prospects (2019) by US National Academy of Sciences.

One of the most important challenges in the NISQ era is to achieve the quantum supremacy (i.e. solving practical or impractical problem(s) which cannot be tractable on the classical computers).  To achieve the goal, it is very important to develop new ideas by taking  interdisciplinary approach with the group of researchers of different background.

The purpose of the present working group is study the issues of quantum computation through a cooperative effort by the experts in theoretical quantum physics, computational science and mathematics. We have three facilitators;  Tetsuo Hatsuda (iTHEMS) who is an expert of the quantum many-body problems in gauge theory, Hidetoshi Nishimori (TIT) who is a discoverer of quantum annealing and is one of the founding fathers of QC , and Seiji Yunoki (R-CCS) who is an expert of computational approaches to quantum many-body problems.  We have also experts from related fields (gauge/gravity correspondence, lattice gauge theory, nuclear many-body problems, open quantum systems, machine leaning, number theory, operator algebras) who have great interests in quantum computation as well as quantum information.

   Half of the present members have already gathered at the RIKEN-Berkeley Workshop on Quantum Information Science (RB19)(Jan.25-20, 2019, Berkeley, USA) with Chia Cheng Chang (iTHEMS/LBNL) as a chair.   In the near future, we will invite more theorists not only from academia but also from industries.

 The field of QC is rapidly growing and progressing, sharing updated knowledge among the members through regular meetings or lectures is very important.  The workshop RB19 mentioned above is considered to be one of such meetings. Also, we had three-day iTHEMS lecture on quantum computation at RIKEN by Dr. Shunji Matsuura (1QBit, Canada) on May 13-15, 2019.  These events had already tremendous impact on the mutual interactions among the members, so that we would like to continue such activities in Wako, Kobe and Berkeley under the support of the iTHEMS working group system.