Circuit quantum electrodynamics

Abstract

Quantum mechanical effects at the macroscopic level were first explored in\nJosephson junction-based superconducting circuits in the 1980's. In the last\ntwenty years, the emergence of quantum information science has intensified\nresearch toward using these circuits as qubits in quantum information\nprocessors. The realization that superconducting qubits can be made to strongly\nand controllably interact with microwave photons, the quantized electromagnetic\nfields stored in superconducting circuits, led to the creation of the field of\ncircuit quantum electrodynamics (QED), the topic of this review. While atomic\ncavity QED inspired many of the early developments of circuit QED, the latter\nhas now become an independent and thriving field of research in its own right.\nCircuit QED allows the study and control of light-matter interaction at the\nquantum level in unprecedented detail. It also plays an essential role in all\ncurrent approaches to quantum information processing with superconducting\ncircuits. In addition, circuit QED enables the study of hybrid quantum systems\ninteracting with microwave photons. Here, we review the coherent coupling of\nsuperconducting qubits to microwave photons in high-quality oscillators\nfocussing on the physics of the Jaynes-Cummings model, its dispersive limit,\nand the different regimes of light-matter interaction in this system. We\ndiscuss coupling of superconducting circuits to their environment, which is\nnecessary for coherent control and measurements in circuit QED, but which also\ninvariably leads to decoherence. Dispersive qubit readout, a central ingredient\nin almost all circuit QED experiments, is also described. Following an\nintroduction to these fundamental concepts that are at the heart of circuit\nQED, we discuss important use cases of these ideas in quantum information\nprocessing and in quantum optics.\n

Keywords

Affiliated Institutions

• Canadian Institute for Advanced Research CA
• Université de Sherbrooke CA

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