Seminar: "Quantum Information Technology in the Near Future --- Hyper-sensitive MRI and Quantum Circuit Learning ---" by Masahiro Kitagawa

I will present two research projects we are currently working on;

1. Hyper-sensitive MRI using triplet-DNP (dynamic nuclear polarization), and
2. Quantum Circuit Learning, and, Quantum Reservoir Computing 

which will be quantum information technology in the near future.
 

i)  Nuclear spins are only slightly aligned even in the strong magnetic fields of superconducting magnets because the magnetic energy of nuclear spin is much smaller than thermal energy. This is the major reason for the difficulty of initializing nuclear spin qubits and the low sensitivity of MRI. By dynamic nuclear polarization (DNP) using photo-excited triplet electrons of pentacene molecule, we have achieved 34% nuclear polarization at room temperature [1], which will make MRI hyper-sensitive and nuclear spin qubits initialized for quantum simulation & computation. We have recently demonstrated dissolution of the sample hyperpolarized by triplet-DNP [2]. The result is an important step for triplet-DNP to become widely used in chemical and biomedical research including MRI.
 

ii)    We propose a classical-quantum hybrid algorithm for machine learning on near-term quantum processors, which we call quantum circuit learning [3]. A quantum circuit driven by our framework learns a given task by tuning parameters implemented on it. The iterative optimization of the parameters allows us to circumvent the high-depth circuit. Theoretical investigation shows that a quantum circuit can approximate nonlinear functions, which is further confirmed by numerical simulations. Hybridizing a low-depth quantum circuit and a classical computer for machine learning, the proposed framework paves the way toward applications of near-term quantum devices for quantum machine learning. We have recently demonstrated quantum machine learning by NMR experiment based on a framework of quantum reservoir computing [4].

References       

[1] Tateishi K, et al., Room temperature hyperpolarization of nuclear spins in bulk, PNAS111 (21), 7527–7530 (2014)

[2] M. Negoro, A. Kagawa, K. Tateishi, Y. Tanaka, T. Yuasa, K. Takahashi, and M. Kitagawa, Dissolution Dynamic Nuclear Polarization at Room Temperature Using Photoexcited Triplet Electrons, J. Phys. Chem. A122 (17), 4294-4297 (2018)

[3] K. Mitarai, M. Negoro, M. Kitagawa, K. Fujii, Quantum Circuit Learning, arXiv:1803.00745

[4] M. Negoro, K. Mitarai, K. Fujii, K. Nakajima, M. Kitagawa, Machine learning with controllable quantum dynamics of a nuclear spin ensemble in a solid, arXiv:1806.10910