Quantum Microwave Sensor

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This project brings atomic physics and cryogenic research together to establish the Geonium Chip as a pioneering, practical quantum technology. The chip's core element is the Coplanar Waveguide Penning trap, conceived and developed by the PI at the University of Sussex. It has a broad range of applications, including quantum computation and metrology, mass spectrometry and the physics of strongly correlated electrons. The project will focus on one concrete goal: the implementation of a broadband, tuneable, quantum non-demolition detector of single microwave photons.An efficient detector of single microwave (MW) photons is a fundamental tool still missing in quantum technology. Such detectors are essential for determining the quantum state of GHz radiation fields and thus vital for quantum communication/information applications with microwaves. While several alternatives based upon super- and semiconductor technologies are being developed, the first observations of individual microwave photons employed a trapped electron as transducer. We will develop the electrons as functional sensors, with unique capabilities for the observation and coherent manipulation of quantum MW fields, initially within the frequency range 3-60 GHz.Cryogenic Penning traps permit an accurate control of the dynamics of a trapped electron, at the level of inducing and observing quantum jumps between its Fock-states. The rest gas pressure in cryogenic vacuum chambers amounts to 10^(-16) mbar, allowing for a very prolonged capture (months) of the particles. The continuous Stern-Gerlach effect permits the detection and manipulation of the electron's spin, while the Purcell effect enhances the coherence time of its quantum state. Hence, cryogenic Penning traps are excellent quantum laboratories and trapped electrons have been proposed for implementing a quantum processor. A single electron in a Penning trap is also known as a geonium atom, as coined by the 1989 Nobel laureate Hans Dehmelt. It is outstanding for ultra-high precision metrology. Examples are the free electron's g-factor, measured with 10^(-13) relative uncertainty and the proton-to-electron mass ratio with 10^(-10). These, and other advanced Penning trap experiments, invariably employ a big, "room-size", superconducting solenoid. We propose to radically change that concept: integrating the trap and the magnetic field source in a single, scalable (2nd generation) Geonium Chip.Within this project we will develop the 2nd generation Geonium Chip into a practical quantum technology. A functional microwave photon detector must provide the following critical features: a) A tuneable, broadband detection range b) Quantum Non Demolition detection c) High quantum efficiency d) Coherent connectivity to other systems e) Scalability and a cost as low as possible. The currently most advanced Penning traps use superconducting solenoids, requiring highly specialised engineers to tune the trapping magnetic field -and hence the detection range-. Moreover, cooling to 100 mK or lower is done with extremely expensive (> £ 350 000) dilution refrigerators, difficult to install and operate. This contrasts radically with our novel Geonium platform, which will eliminate solenoid and dilution refrigerator altogether. With this pioneering approach, we will reduce the cost and complexity, enabling our chip Penning trap as a useful quantum 2.0 technology, particularly as a single microwave photon detector.