RAISE-TAQS: Symmetry Protected Quantum Bits through Fluxon Pairing

点击翻译按钮获取中文摘要

Non-technical description: With the current pace of quantum technology development, the realization of a superconducting quantum computer is fast approaching. Quantum computers offer the possibility for exponential speedup in computation in comparison to classical computers on some of the hardest problems relevant to humanity today. Over the past decade, the performance of the elements of a quantum computer, the quantum bit (qubit) has improved tremendously. Despite this progress in performance, it has been shown that there is still a long way to go in improving qubit performance to realize a practical quantum computer. The goal of this project is to design, fabricate, and characterize a new class of fault-tolerant logical qubits for a quantum computer decoupled from the environment and protected from local noises. The logical qubit is based on incorporating error correction at the hardware level utilizing nontrivial symmetries and engineering quantum mechanical interactions in the circuit which makes up the qubit. This research project contributes to a better understanding of how certain quantum interactions which have typically not been exploited in quantum computers can be utilized to improve qubit performance and scalability. The educational outreach portion of this project addresses the need to train future quantum electronics engineers for positions which are currently in high demand in the quantum technologies industry encompassing both tech industry giants and a quantum startup ecosystem. Such activities encompass the introduction of a series of short courses on introductory quantum information sciences targeted at physics and electrical engineering students early on in their careers, exposing them to opportunities in the ever-expanding quantum technology industry.Technical description: The project investigates transformative ideas of realizing highly coherent qubits through symmetry-protection of a quantum state encoded in the parity of fluxons in a superconducting loop. The proposed qubit provides a Hamiltonian realization of an error correction code where the ground states of the Hamiltonian can be regarded as the logical basis states. The realization of a full-fledged topologically protected quantum state in a circuit has been elusive primarily because alternative approaches have required elements not found in the conventional superconducting circuit toolbox. This project utilizes two newly developed circuit elements, the charge-based quantum interference device and a superinductor, to realize a protected fluxon-pairing quantum circuit, a cos(phi/2) Josephson element whose lowest-energy states are different by the parity of fluxons in a superconducting loop. It is expected that such a circuit could be decoupled from local noises and demonstrate very long coherence in the protected state. The objectives of this project are: (1) to develop a highly coherent fluxon-pairing qubit by first enhancing the Aharonov-Casher interference through symmetry improvements in the design of the qubit; (2) to further develop superinductor technology; (3) to demonstrate protection against energy relaxation and de-coherence in the protected state of the fluxon-pairing qubit; (4) to demonstrate fast adiabatic switching between the protected and unprotected states for state preparation and measurement operations; and (5) to demonstrate fault-tolerant single and two-qubit gate operations on the sub-microsecond time scale. The project also supports the education of graduate students who enjoy broad exposure to the state-of-the-art tools of modern quantum information research. The multi-component educational and outreach component, an essential part of the project, is designed to develop a program to train future quantum electronics engineers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.