- The method can produce an extremely sensitive photon detector operating in the microwave range that is able to detect single microwave photons propagating in a metallic waveguide.
- Antenna applications
- Quantum calculation
- Microwave applications
- Ultrasensitive spectrum analyzer
The present invention introduces a detector that is able to detect single microwave photons propagating in a waveguide. The waveguide of the invention is lowered to a temperature where it becomes superconductive. Disposed between middle wire and a ground plane of the waveguide is a very small piece of a desired normal metal, whereby so-called SN contacts are formed between these materials. A separate reflection measurement circuit is coupled to the normal metal piece. When the impedance of the waveguide is matched to the impedance of the normal metal piece as well as possible, a photon propagating in the waveguide is most likely absorbed in the normal metal. The absorption slightly raises the temperature of the piece, which further changes the impedance observed in a so-called SIN junction between the reflection measurement circuit and the piece. The changed amplitude and phase are detectable at the outlet obtained from a mixer of the reflection measurement circuit, whereby a single absorbed photon can be detected. In principle, the present method and device enable quantum calculation in view of future applications.
Detecting single microwave photons in a metallic waveguide (10) comprises creating microwave photon(s) in the waveguide disposed in a superconductive state; directing microwave photon(s) from the waveguide to a resistive element (11) in a manner as free of losses as possible; and measuring, by a reflection measurement circuit (18), a change of impedance in a junction between the resistive element and the reflection measurement circuit due to heating of the resistive element. The method further comprises using a normal metal piece, semiconductor nanowire, graphene piece or carbon nanotube as the resistive element.
Based on experimental data with continuous and pulsed waves, our latest prototype device shows a quantum efficiency above 50% for single photons and a good fidelity for observing single photons in the range of hundreds of gigahertz.
Priority date: 20.09.2010
Main inventor: Dr. Mikko Möttönen
Department of Applied Physics
Head of Innovation Services
Phone: +358 40 186 3320