Quantum information processing with bosonic qubits in circuit QED

Abstract

The unique features of quantum theory offer a powerful new paradigm for information processing. Translating these mathematical abstractions into useful algorithms and applications requires quantum systems with significant complexity and sufficiently low error rates. Such quantum systems must be made from robust hardware that can coherently store, process, and extract the encoded information, as well as possess effective quantum error correction (QEC) protocols to detect and correct errors. Circuit quantum electrodynamics (cQED) provides a promising hardware platform for implementing robust quantum devices. In particular, bosonic encodings in cQED that use multi-photon states of superconducting cavities to encode information have shown success in realizing hardware-efficient QEC. Here, we review recent developments in the theory and implementation of QEC with bosonic codes and report the progress made toward realizing fault-tolerant quantum information processing with cQED devices.

Phase-engineered bosonic quantum codes

“…Meanwhile, progress in superconducting circuit quantum electrodynamics (cQED), e.g., real-time adaptive control [13], fault-tolerant readout of excitation parity [18,19], and universal control of cavity [20][21][22][23], has opened up possibilities once thought unreachable, including implementing arbitrary quantum channels [24,25]. With the advances, errorcorrected cat and bin qubits and the associated universal gate sets have been demonstrated [13,[26][27][28][29]. These capabilities together make possible higher-level tasks with bosonic systems, such as gate teleportation [30] and distributing errorcorrected entangled states [31].…”

Extending superconducting qubit lifetimes: What’s Next?

“…Bosonic encoding [13][14][15][16] offers a number of crucial advantages over qubit encodings and there are now several experiments [17][18][19][20][21] that have approached or slightly exceeded the break-even point. In bosonic encodings, the logical quantum information is encoded in superpositions of different Fock states (of microwave photons stored in superconducting cavities, or in the mechanical oscillations of trapped ions or trapped phonons in solids).…”

Time-varying quantum channel models for superconducting qubits

“…It is important to point out that the aforementioned QECCs are utilized in the context of conventional qubit-based quantum computation, in which the physical elements are realized by discrete two-level systems. Other promising routes toward universal quantum computation and error correction exist, such as bosonic codes 14,15 . In this paper, we focus on error correction based on two-level physical constructions, and all the discussions refer to this specific approach to QECC.…”