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This study presents a breakthrough in quantum hardware by demonstrating the first non-superconducting, near-quantum-limited maser amplifier operating at millikelvin temperatures using diamond nitrogen impurity spins. By achieving over 30 dB gain with minimal added noise, this device offers a complementary pathway to superconducting technologies for critical applications like spin-qubit readout and dark-matter axion searches. The ability to function in strong static magnetic fields of arbitrary orientation further expands the toolkit for next-generation quantum sensing and computing architectures.
A near-quantum-limited diamond maser amplifier operating at millikelvin temperatures
arXiv:2505.05705v2 Announce Type: replace Abstract: Current microwave quantum technologies require the amplification of weak signals with minimal added noise at millikelvin temperatures. To date, this stringent requirement has been met exclusively by superconducting technologies, such as Josephson or kinetic-inductance parametric amplifiers. A fundamentally distinct alternative approach could be offered by masers, the microwave counterpart of lasers, which were predicted as early as the 1950s to achieve quantum-limited noise performance under ideal conditions. However, their dependence on cryogenic operation historically limited further advancement. Here we demonstrate the first-ever non-superconducting, near-quantum-limited maser amplifier operating at millikelvin temperatures utilising nitrogen impurity spins (P1 centres) in diamond. Population inversion is achieved via microwave pumping, exploiting a four-spin cross-relaxation mechanism. We realise a maximum power gain exceeding 30 dB, an added noise of approximately 2.55 quanta above the standard quantum limit, and a maximum 1 dB output compression point of -63 dBm at 6.595 GHz. The ability to operate in strong static magnetic fields of arbitrary orientation may offer a complementary, non-superconducting route for applications such as semiconducting spin-qubit readout, magnetic-resonance spectroscopy, and dark-matter axion searches.
Authors:Morihiro Ohta, Ching-Ping Lee, Vincent P.M. Sietses, Ivan Kostylev, Jason R. Ball, Petr Moroshkin, Tatsuki Hamamoto, Yutaka Kobayashi, Shinobu Onoda, Takeshi Ohshima, Junichi Isoya, Hiroki Takahashi, Yuimaru Kubo
Abstract:Current microwave quantum technologies require the amplification of weak signals with minimal added noise at millikelvin temperatures. To date, this stringent requirement has been met exclusively by superconducting technologies, such as Josephson or kinetic-inductance parametric amplifiers. A fundamentally distinct alternative approach could be offered by masers, the microwave counterpart of lasers, which were predicted as early as the 1950s to achieve quantum-limited noise performance under ideal conditions. However, their dependence on cryogenic operation historically limited further advancement. Here we demonstrate the first-ever non-superconducting, near-quantum-limited maser amplifier operating at millikelvin temperatures utilising nitrogen impurity spins (P1 centres) in diamond. Population inversion is achieved via microwave pumping, exploiting a four-spin cross-relaxation mechanism. We realise a maximum power gain exceeding 30 dB, an added noise of approximately 2.55 quanta above the standard quantum limit, and a maximum 1 dB output compression point of -63 dBm at 6.595 GHz. The ability to operate in strong static magnetic fields of arbitrary orientation may offer a complementary, non-superconducting route for applications such as semiconducting spin-qubit readout, magnetic-resonance spectroscopy, and dark-matter axion searches.
Main text: 7 pages, 4 figures. Supplementary Materials: 18 pages, 9 figures
arXiv:2505.05705 [quant-ph]
(or arXiv:2505.05705v2 [quant-ph] for this version)
Full text under the publisher's open licence · 224 words
