LEAPS-MPS: Multiqubit Entangling Gates for Solid-State Qubit Systems

Quantum information science and quantum computing have become the forefront of future science and technology. Quantum computing promises a great leap forward from classical computing capabilities. However, the current quantum hardware has only a modest number of qubits (hundreds of qubits in a single device) and limited coherence, making it difficult to use for practical problems. In this project, the PI will address some of the above limitations by investigating alternative ways to implement quantum operations on quantum hardware by creating entanglement - an essential resource for quantum computation - between more than two qubits more efficiently than the standard approach. This approach can reduce the depth of the quantum circuits and extend the usefulness of the limited quantum hardware. This new method will be applied to some hybrid quantum-classical algorithms that many consider the leading practical applications of quantum computers in the near future. As quantum technology progresses and its importance increases, a larger quantum workforce will be essential for maintaining the competitive edge, and it is important to engage underrepresented demographic groups in quantum science and technology. This project will provide valuable research experiences to graduate and undergraduate students at the University of Texas at El Paso who will join the quantum workforce in academia, industries, and national labs. Quantum computation requires creating entanglement using entangling gates between qubits to generate highly entangled many-qubit states. The standard approach for implementing quantum circuits is to use single- and two-qubit gates that can generate any quantum circuits in principle. However, creating entanglement only using two-qubit gates typically results in a very long sequence of quantum gates for any practical quantum circuits. This project investigates possible multiqubit entangling gates for more than two qubits in solid-state-based qubit platforms of semiconductor spin qubits and superconducting qubits. This project will consider two schemes to generate multiqubit gates: (i) simultaneous application of pairwise interactions between qubits and (ii) multiqubit interactions mediated by a common bus where more than two qubits are connected simultaneously. Theoretical analysis of the physical qubit platforms and numerical simulation of the quantum gates and quantum circuits throughout the project will shed light on the efficiency of quantum circuits made of multiqubit gates in implementing quantum algorithms, especially hybrid quantum algorithms such as variational quantum eigensolver. The new approach developed in this project can lead to useful applications of the currently available quantum computing devices for practical problems, such as simulating complex quantum systems beyond the capability of classical computation. 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.