Quantum Microwave Sensor

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.

1 Application and exploitation. Two patents protect the intellectual property on the Geonium Chip: US 8,362,423 B1 and WO 2013/041615 A2. The anticipated economic impacts in mass spectrometry and in quantum technology are the main motivations. In the case of mass spectrometry, which is a very mature market, our strategy is to first demonstrate experimentally the advantages of our technology, making it more valuable to prospective stakeholders.

Scientific Advisory Board. In the case of quantum technology 2.0, particularly for single MW photon detection, the market is still inexistent. The Geonium Chip will be ready to be used as a MW sensor by Year 4. Thus, within the given time frame of total 5 years we will investigate one practical application among the many potential uses. At this point it is still open what particular application we will focus on (options given in WP4). We will build one single device, hence it is critical to have interested users on board from day 1 of the project. Through their vital input on potential uses in their sectors, we will be able to make the pertinent design and construction plans -within the general technical boundaries described in the Case for Support- to meet the specified requirements. For this reason our strategy is to incorporate DSTL, BAE Systems and Selex ES as advisors to the project. We will form a Scientific Advisory Board with the following members: PI (Verdu) + Co-I (Hepburn) + Sussex industry liaison officer (Colin Hayhurst) + DSTL + BAE Systems + Selex ES. Other academics and/or industrial partners will be eventually invited later to join the advisory board. This will meet regularly, at least twice per year, mostly at Sussex but also at MSSL and other locations. The PI will chair the meetings. In addition to the participation in the board, DSTL will provide access to trial facilities for testing our MW sensor in realistic scenarios.

Dissemination. We plan to attend the following conferences (in some editions during the fellowship): European Conference on Trapped Ions ECTI (held every 2nd year), European Conference on Atoms and Photons ECAMP (every third year), International Conference on Atomic Physics ICAP, Cryogenic Engineering Conference CEC and Low Temperature Detector conference LTD (all every 2nd year). We will also attend at least one workshop per year on any of the relevant areas. In total 12 events (5 conferences + 5 workshops + 2 meetings) are planned to boost the impact.

2 Communications and engagement. Deliverable D1 is expected to be published in Physical Review Letters or similar. Deliverable D2 expected to appear in Nature, Science or similar. Furthermore, the domain www.geoniumchip.org has been registered for dissemination of our research. This web page will provide useful files for downloading. In particular, we will offer a full interactive calculator/simulator of planar Penning traps, based upon the free software Wolfram CDF player. This will contribute to increase the visibility of the page and also the number of citations and impact of our results. We also plan to record some demonstration videos explaining and showing "live" our activities.

3 Collaboration and coproduction. A planned collaboration with the group of Prof Dr F Schmidt-Kaler in Mainz (www.quantenbit.de) is aimed at developing into a future formal European network (a collaborative project of Horizon 2020 or future equivalent) in which our group will assume a leading role.

4 Capacity and involvement. The PI and Co-I will be the main persons for impact activities, particularly for presentations in conferences, visiting other groups, networking and outreach. The requested PDRA will participate in one international conference/workshop per year and will also be involved in networking and outreach.