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IEEE Transactions on Microwave Theory and Techniques

Quantum-Based Microwave Power Measurements: Proof-Of-Concept Experiment | NIST

T. P. Crowley, Elizabeth A. Donley, Thomas P. Heavner

Published Aug 1, 2004• 0 citations
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Quantum-based microwave power measurements: Proof-of-concept experiment

T. P. Crowley, Elizabeth A. Donley, Thomas P. Heavner

We present an initial proof-of-concept experiment to measure microwave power based on quantum-mechanical principles. Ground-state cesium atoms exposed to microwaves at 9.192 631 770 GHz oscillate between two hyperfine states at a rate that is proportional to the rf magnetic field strength. This provides a quantum-based method of measuring rf field strength that depends only on the fundamental parameters in the proportionality constant. A small fountain apparatus was used to prepare laser-cooled cesium atoms in a single hyperfine state, which were then launched through a cylindrical cavity operating in the TE011 mode. After passing through the cavity, the fraction of atoms in the two hyperfine states was measured. Rabi oscillations between the two states were observed as a function of microwave field strength. The scaling with field strength and with time in the cavity agreed with theory to within 0.4%. The field strength in the cavity was used, together with measured S parameters, to determine the microwave power incident at a reference plane outside the fountain apparatus. The difference between the quantum-based microwave power measurement and a traditional microwave power measurement was less than 5% of the measured power.

Review of Scientific Instruments•Jul 27, 2004•38 citations

Development of a quantum based microwave power measurement

T. P. Crowley, Elizabeth A. Donley, Thomas P. Heavner +2 more

An initial proof-of-principle experiment to measure microwave power based on quantum mechanical principles is presented. An RF magnetic field causes laser-cooled cesium atoms to oscillate between two hyperfine levels at a rate proportional to the field strength. The populations vary as predicted with relative microwave intensity and duration.

IEEE MTT-S International Microwave Symposium digest•Aug 27, 2003•1 citation

Radiative Cooling of a Superconducting Resonator

Mingrui Xu, Xu Han, Chang‐Ling Zou +5 more

Cooling microwave resonators to near the quantum ground state, crucial for their operation in the quantum regime, is typically achieved by direct device refrigeration to a few tens of millikelvin. However, in quantum experiments that require high operation power such as microwave-to-optics quantum transduction, it is desirable to operate at higher temperatures with non-negligible environmental thermal excitations, where larger cooling power is available. In this Letter, we present a radiative cooling protocol to prepare a superconducting microwave mode near its quantum ground state in spite of warm environment temperatures for the resonator. In this proof-of-concept experiment, the mode occupancy of a 10 GHz superconducting resonator thermally anchored at 1.02 K is reduced to 0.44±0.05 from 1.56 by radiatively coupling to a 70 mK cold load. This radiative cooling scheme allows high-operation-power microwave experiments to work in the quantum regime, and opens possibilities for routing microwave quantum states to elevated temperatures.

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Quantum Microwave Measurements

Yashika Aneja, Monika Thakran, Asheesh Kumar Sharma +2 more

Springer eBooks•Jan 1, 2023•0 citations
We present an initial proof-of-concept experiment to measure microwave power based on quantum-mechanical principles. Ground-state cesium atoms exposed to microwaves at 9.192 631 770 GHz oscillate between two hyperfine states at a rate that is proportional to the rf magnetic field strength. This provides a quantum-based method of measuring rf field strength that depends only on the fundamental parameters in the proportionality constant. A small fountain apparatus was used to prepare laser-cooled cesium atoms in a single hyperfine state, which were then launched through a cylindrical cavity operating in the TE011 mode. After passing through the cavity, the fraction of atoms in the two hyperfine states was measured. Rabi oscillations between the two states were observed as a function of microwave field strength. The scaling with field strength and with time in the cavity agreed with theory to within 0.4%. The field strength in the cavity was used, together with measured S parameters, to determine the microwave power incident at a reference plane outside the fountain apparatus. The difference between the quantum-based microwave power measurement and a traditional microwave power measurement was less than 5% of the measured power.
Cooling microwave resonators to near the quantum ground state, crucial for their operation in the quantum regime, is typically achieved by direct device refrigeration to a few tens of millikelvin. However, in quantum experiments that require high operation power such as microwave-to-optics quantum transduction, it is desirable to operate at higher temperatures with non-negligible environmental thermal excitations, where larger cooling power is available. In this Letter, we present a radiative cooling protocol to prepare a superconducting microwave mode near its quantum ground state in spite of warm environment temperatures for the resonator. In this proof-of-concept experiment, the mode occupancy of a 10 GHz superconducting resonator thermally anchored at 1.02 K is reduced to 0.44±0.05 from 1.56 by radiatively coupling to a 70 mK cold load. This radiative cooling scheme allows high-operation-power microwave experiments to work in the quantum regime, and opens possibilities for routing microwave quantum states to elevated temperatures.