Quantum sensing

Advancing Astrophysics with Single-Photon Detection

Image adapted from Pierre Echternach, 2024, "A Hybrid Quantum Capacitance-Kinetic Inductance Detector". 3 Presto units are synchronized using a Metronomo to readout 441 single photon detectors using the Lockin mode. On the right, the acquired quadrature data (a), and processed data (b) and (c) where red circles indicate the detection of a single photon.

Introduction:
NASA's Jet Propulsion Laboratory (JPL) is developing advanced sensors for space exploration and scientific research. One exciting area of their work is single photon detectors (SPD). They research two kinds of SPD: quantum capacitance detectors (QCDs) and hybrid kinetic inductance-quantum capacitance detectors (Hybrid KID-QCD). These sensors are designed to detect single photons, the fundamental particles of light. Using Intermodulation Products instruments Presto and Metronomo they are able to measure large arrays of SPD.

Quantum Capacitance Detectors
QCDs use a superconducting island connected to a ground electrode via a tunnel junction. When a photon strikes the detector, it breaks Cooper pairs (paired electrons), creating quasiparticles (unpaired electrons). These quasiparticles tunnel onto the island, changing its capacitance. This change in capacitance is then detected by embedding the QCD in a resonator, where the change in capacitance shifts the resonance frequency.

Single-Photon Counting with QCDs
QCDs have demonstrated the ability to detect single photons, as shown in experiments at JPL. By analyzing the raw quadrature response of the detector, researchers can identify single-photon detection events.

Overcoming QCD Limitations with Hybrid KID-QCD
While QCDs offer high sensitivity, they have a limited dynamic range. To address this, JPL is developing a hybrid QCD that combines the high sensitivity of QCDs with the broader dynamic range of kinetic inductance detectors (KIDs). This hybrid approach allows for more accurate measurements over a wider range of optical powers.

Intermodulation Products' Role
Intermodulation Products has been instrumental in supporting JPL's research in this area. Our instruments Presto and Metronomo have been used to measure the response of QCDs. The Lockin mode has enabled precise measurements of the quantum capacitance amplitude and the detection of single-photon events.

The Future: Spectral Mode for Large-Scale SPD Arrays
To further advance SPD technology, we have developed a new measurement mode called Spectral. This mode will enable the measurement of large arrays of different kinds of SPDs. Using Spectral mode, one Presto is able to measure thousands of sensors. This development will significantly enhance the capabilities of SPDs, opening up new possibilities for their use in various scientific fields.

Conclusion
Intermodulation Products is proud to be supporting cutting-edge research at NASA's Jet Propulsion Laboratory in the development of single photon detectors. Our instruments and the new Spectral mode are contributing to the advancement of this exciting technology, paving the way for groundbreaking discoveries in astrophysics and other fields.