(Nanowork News) Scientists at Paderborn University have used a new method to determine the properties of optical, i.e. light-based, quantum states. For the first time, they are using specific photon detectors – devices that can detect individual light particles – for so-called homodyne detection. The ability to characterize optical quantum states makes this method an essential tool for quantum information processing. Accurate knowledge of their properties is important, for example, for use in quantum computers.
The results were published in the journal. quantum optics (“Low-noise balanced homodyne detection using a superconducting nanowire single-photon detector”).
“Homodyne detection is a frequently used method in quantum optics to probe the wave properties of optical quantum states,” explains Timon Schapeler from the Paderborn “Mesoscopic Quantum Optics” working group at the Department of Physics. Together with Dr. Maximilian Protte, he used this method to investigate continuous variables in optical quantum states. This includes various characteristics of light waves. This could be, for example, the amplitude or phase, i.e. the oscillatory behavior of the wave, which is important, among other things, for the targeted manipulation of light.
For the first time, physicists used a superconducting nanowire single-photon detector for their measurements, which is currently the fastest device for photon counting. Through a special experimental setup, the two scientists showed that a homodyne detector with a superconducting single-photon detector exhibits a linear response to the input photon flux. Translated, this means that the measured signal is proportional to the input signal.
“In principle, the integration of a superconducting single-photon detector offers many advantages in the continuous variable region, especially in the intrinsic phase stability. The system also has an on-chip detection efficiency of almost 100%, meaning no particles are lost. “Our results could enable the development of highly efficient homodyne detectors with single-photon detection detectors,” says Schapeler.
Using the continuous variable of light opens up new and exciting possibilities for quantum information processing beyond qubits, the typical computing units in quantum computers.