Quantum Interface Between Atomic and Superconducting Qubits

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While there has been tremendous recent progress in the realization of small-scale quantum circuits comprising several qubits, research indicates that a fault-tolerant quantum computer that exceeds what is possible on existing classical machines will require a network of thousands of qubits, far beyond current capabilities. One possible approach involves a hybrid quantum information processing (QIP) network that would capitalize on the unique strengths of disparate quantum technologies. Here we outline a research program focused on the development of a robust quantum interface between superconducting cavity circuits and trapped Rydberg atoms, the key technological obstacle to realization of atom-superconductor hybrid QIP. The research program includes the following specific experimental thrusts: single atoms will be trapped and guided into close proximity with a millikelvin-temperature superconducting thin-film cavity; strong coupling between single trapped Rydberg atoms and the cavity will be probed spectroscopically; and deterministic generation of single microwave photons by a superconducting qubit will be used to enable an entangling gate between the atomic and superconducting systems. The development of a high-fidelity quantum interface between a trapped atom qubit and a superconducting microwave cavity will represent a significant step towards a hybrid quantum computer. This program will involve the extensive participation of undergraduate and graduate researchers, and is rich in educational opportunities at both levels.One of the remarkable recent discoveries in information science is that quantum mechanics can lead to efficient solutions for problems that are intractable on conventional classical computers. In a quantum computer, information is stored in quantum bits or "qubits" that can exist not only in states 0 or 1, but also in arbitrary superpositions of these states. Robust operation of a quantum computer requires both long lifetimes for these quantum superpositions, along with the ability to interact qubits with one another on timescales that are much shorter than the qubit lifetime. For a given system of physical qubits, the requirements of long lifetime and fast interaction speed are generally at odds with one another. One possible approach to scalable quantum computing involves an optimized hybrid quantum processor that combines the best aspects of disparate quantum technologies. In this program, we are working toward a hybrid quantum processor that incorporates a stable neutral atom quantum memory, with storage times of order 1 second, and a fast superconducting quantum processor capable of interacting qubits on timescales of order 10 nanoseconds. We seek to address the key obstacle to the merger of neutral atom and superconducting quantum technologies, namely, a robust interface between trapped atomic qubits and superconducting quantum cavities. Successful realization of our program will represent a major step toward scalable hybrid quantum information processing. This program will involve the extensive participation of undergraduate and graduate researchers, and is rich in educational opportunities at both levels.