MRI used to control multiple quantum bits in diamond

孝明 下岡

Norikazu Mizuochi

Z. H. Cho, Jihye Han, Dae‐Hwan Suk +5 more

We propose a novel MRI (Magnetic Resonance Imaging) technique based quantum bit (qubit) generation with water proton NMR (1H-NMR), distinct from previously proposed NMR chemical shift or spectroscopic techniques based qubit generation. We briefly review prior NMR-based techniques in the context of quantum computing, focusing on MRI-related methods. The proposed technique utilizes MRI-based gradient methods combined with set of local reverse gradients to generate multiple qubits. This configuration enables the creation of multiple localized constant magnetic fields, each producing a qubit with highly homogeneous field, therefore, a unique single frequency. The RF electronics and signal processing techniques are analogous to those used in conventional MRI scanners, allowing operation at room temperature, with the exception of the main magnet, which remains identical to that of standard MRI systems. Additional advantages of this method include the ability to leverage the extensive pulse techniques and hardware developed for MRI scanners over the past 50 years. Furthermore, the wide array of MRI pulse sequences enables highly sophisticated signal processing for quantum computing applications, such as the spin purification.

D.M. Toyli

Santiago Hernández-Gómez, Federico Balducci, Paola Cappellaro +2 more

The nitrogen-vacancy (NV) center in diamond is a quantum defect in diamond with unique properties for use in high-sensitive, high-resolution quantum sensors of magnetic fields. One of the most interesting and challenging application of NV quantum sensors is nanoscale magnetic resonance imaging (nano-MRI), which would enable to address single biomolecules. To this goal, improving the sensitivity of the NV sensor is a crucial task. Here, we present a quantum optimal control method that optimizes the sensitivity of NV sensor to specific weak magnetic signals with biologically-relevant, complex spectrum. The method, based on the mapping of the sensing problem on a problem of energy optimization of an Ising chain, allows us to improve sensitivity by three orders of magnitude compared to standard control sequences.

Zang‐Hee Cho, Young‐Don Son, Hyejin Jeong +4 more

Explosive increase of interest in quantum computing has resulted in various proposals for generation of quantum bits or qubits, the basic quantum computing unit. The superconducting qubits of Josephson Junction are the most widely accepted and currently used, while the Ion-trap and a similar molecule-based qubits have been proposed more recently. In these methods, each qubit is generated individually with great effort. Here we proposed a new technique using magnetic resonance imaging (MRI)-based qubit generation, by which multiple qubits can be generated. Simultaneously this provides a complete qubit platform for quantum computing. Central to the proposed method is the simultaneous generation of multiple qubits using the 'gradient' concept together with multiple radiofrequency coils, one for all qubits, and others for individual qubits with each small Q-coil. Another key concept is the time-encoded probability amplitude (TEPA) technique, using individual Q-coils together with the spin-echo series in each qubit incorporating readout gating for time-encoding. This MRI-based qubit-generation and qubit-encoding technique allowed us to develop an entirely new class of quantum computing platform. Our newly proposed MRI-based qubits are well-suited to currently available electronics, superconducting and semiconductor technologies, as well as nuclear magnetic resonance and MRI physics and technology.