Microwave Quantum Photonics in Superconducting Systems
Summary
Microwave quantum photonics in superconducting platforms brings together the fields of circuit quantum electrodynamics and low-temperature photonics to generate, manipulate and detect individual quanta of the microwave electromagnetic field. Superconducting circuits incorporating Josephson junctions provide strong nonlinearity and coupling between artificial atoms (qubits) and on-chip resonators or transmission lines. This enables the deterministic emission of single microwave photons, coherent control of itinerant quantum states and quantum-limited amplification. Cryogenic nanobolometers and parametric amplifiers permit direct measurement of photon statistics and correlations at millikelvin temperatures, overcoming thermal noise and classical amplification noise. Progress in near-field microwave microscopy, correlation measurements and on-demand photon sources is paving the way for scalable quantum networks, distributed superconducting quantum processors and quantum sensing applications such as microwave quantum radar and quantum key distribution. The integration of high-coherence superconducting elements with microwave photonic circuits underpins emerging technologies for secure communication, fundamental tests of quantum mechanics and the realisation of modular architectures in quantum computing.
Research from Nature Portfolio
Recent studies have achieved direct correlation measurements of propagating microwave photons using a novel cryogenic nanobolometer. By coupling a temperature-controlled blackbody source to the detector at millikelvin temperatures, researchers have extracted both mean photon numbers and second-order correlations, confirming Bose–Einstein statistics for thermal fields and demonstrating transitions between super-Poissonian and Poissonian regimes. Another foundational work has implemented an impedance-matched three-level artificial system to detect single microwave photons in a waveguide. Each photon triggers a Raman transition in a driven superconducting qubit–resonator pair, yielding a discrete readout with high efficiency and low dark-count rates. These advances establish versatile, scalable readout schemes for quantum information processors and precise tests of microwave quantum optics.
Microwave Quantum Photonics in Superconducting Systems publication trend
The graph below shows the total number of articles in microwave quantum photonics in superconducting systems across all publications each year (not limited to Nature Index journals).
Technical terms
Microwave photon: A quantum of the electromagnetic field at gigahertz frequencies, carrying discrete energy ℏω in the microwave regime.
Superconducting qubit: An engineered two-level system formed by Josephson junction circuits, offering long coherence times and tunable interactions with microwave fields.
Josephson junction: A superconducting weak link whose non-linear inductance enables parametric amplification, photon detection and quantum state control.
Nanobolometer: A cryogenic thermal sensor that measures minute temperature changes induced by microwave photon absorption, enabling correlation and energy-resolved detection.
Parametric amplifier: A non-linear device that amplifies an input signal by modulating circuit parameters (such as inductance) at a pump frequency, achieving near-quantum-limited gain.
References
- Correlation measurement of propagating microwave photons at millikelvin. Nature Communications (2025).
- Ultra-broadband near-field Josephson microwave microscopy. National Science Review (2024).
- Microwave Photon Detection at Parametric Criticality. PRX Quantum (2024).
- Propagating quantum microwaves: towards applications in communication and sensing. Quantum Science and Technology (2023).
- Single microwave-photon detector using an artificial Λ-type three-level system. Nature Communications (2016).
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