Quantum Error Correction with A Dual Species Atomic Qubit Array

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Quantum computing is attracting great interest due to its potential for solving practical problems that are intractable on classical computers. Areas of application include cryptography, design of new functional materials or chemical compounds, and speed up of machine learning systems for artificial intelligence using quantum mechanical phenomena. Today’s classical computers are extremely reliable because they incorporate circuitry for correcting infrequent, but unavoidable electronic errors before they disrupt the operation of the computer. For quantum computers to achieve their full potential they will also need error correcting circuitry. Correcting errors on a quantum computer is much more difficult than correcting errors on a classical computer because quantum states have a continuous range of values, not just the binary 0 or 1 of a classical computer. This project will demonstrate new approaches to implementing error correction on a quantum computer. The approach will use two different atomic elements, with one element holding the data to be protected while the other element will be used to detect errors that occur. When an error is detected operations will be applied to the data to correct the errors. These ideas will be demonstrated experimentally in a prototype, small scale quantum computer with error correction. Aditionally the project will contribute to scientific workforce development through training of students. The training will be interdisciplinary, drawing on methods and ideas from atomic and laser physics, electronic and computer based control systems, and quantum information theory. Research results will be incorporated into the University teaching curriculum. The project will advance the state of the art in quantum computation using atomic qubits. It will implement novel approaches to quantum error correction using two different atomic elements in a single experiment. A two-species array with data qubits encoded in Cs atoms and ancillas in Rb atoms will be used to demonstrate correction of quantum errors and the protection of encoded logical qubits against decoherence. One of the species (Cs) will be used to encode data qubits. The other species (Rb) will be used as measurement qubits. Quantum information will be transferred from Cs to Rb using a two-species quantum gate, and the Rb atoms will then be measured as part of the error correction protocol. The two-species array will use a novel technique that requires only a single wavelength of trapping light to confine two different atomic elements in spatially interleaved arrays. Quantum logic gates to create entanglement between pairs of atoms of the same type as well as pairs of atoms of different types will be performed by exciting atoms to Rydberg states with laser pulses. The major goals of the project will be to demonstrate preparation of logical qubits using the surface code and the 7-qubit Steane code. The coherence properties of logically encoded states will be studied and gates will be demonstrated between logical qubits. 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.