- 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 information
- Microwave applications
- Ultrasensitive network and spectrum analyzer
The present invention introduces a bolometer that is eventually 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 [between Ports H and G in Fig. 1(a, b)] 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 efficiently absorbed in the normal metal. The absorption slightly raises the temperature of the piece, which further changes the impedance observed in a junction between the Ports P and G in Fig. 1(a, b) in the reflection measurement circuit. The changed amplitude and phase [see Fig.1 (c)] are detectable at the outlet obtained using a microwave mixer, whereby absorbed photons can be detected. In principle, the present method and device enable quantum computing with propagating microwave photons in view of future applications. In experiments, we have shown that this detector has a record breking energy resolution of 1 zJ for thermal detectors. It is naturally broad band and has a demonstrated noise-equivalent power of ~10-20 W/Hz1/2.
Detecting single microwave photons in a metallic waveguide comprises creating microwave photon(s) in the waveguide disposed in a superconductive state; directing microwave photon(s) from the waveguide to a resistive element in a manner as free of losses as possible; and measuring, by a reflection measurement circuit, 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.
Download tech-sheet: IPID 752 Tech Sheet_MM
Based on experimental data with continuous and pulsed waves, our latest prototype device shows a quantum efficiency above 50% for 1-zJ energy (>90% for 5 zJ) and a noise equivalent power of ~10-20 W/Hz1/2.
Priority date: 20.09.2010
Main inventor: Dr. Mikko Möttönen Department of Applied Physics
Phone: +358 50 338 0509