Levitated Electromechanics: All-Electrical Nanoscale Control and Cooling (LEVELECTRO)

**The research in context**

Technology is continuously miniaturizing, and as it reaches the nanoscale we face unique challenges. How do we control such small objects? What happens when temperature fluctuations have the same energy scale as our devices? From the other direction, advances in the quantum physics of a few atoms, ions, and solid-state qubits mean that we increasingly wish to scale up quantum systems, or interface them with nanoscale technology.

Nano- and micro-mechanical devices have been controlled at the quantum level in recent years, an amazing advance allowing even entanglement between light and mechanical motion. However, all such small systems are limited by unavoidable environmental effects, such as thermal contact with the surroundings and energy dissipation through strain. This limits the participation of mechanical devices in both classical and quantum technologies.

By using a levitated nanoparticle as the mechanical device, these problems are overcome. LEVELECTRO will pioneer the integration of levitated nano-objects with electronic circuits, allowing electrical cooling and networking. This ultra-low dissipation system offers exquisite force sensitivity.

LEVELECTRO will explore new regimes of physics, by working in extreme vacuum, elucidating thermodynamics on the nanoscale. This unique research will enable levitated nano-objects to participate in quantum technologies as long-lived quantum storage devices, and as high-fidelity transducers between optical and electronic quantum signals.

**Aims and Applications**

*Aim 1 - All-electrical nanoparticle control platform: LEVELECTRO introduces a new platform, where a levitated nanoparticle is coupled to an electrical circuit, founding the field levitated electromechanics (LE). LE will allow fully electronic control and cooling of the motion of nanoparticles, avoiding the detrimental scattering and absorption encountered in optical levitation. Electrical cooling removes thermal energy which masks the sensitivity of the levitated particles to their environment, hence cooling boosts the ability for the LE platform to behave as a sensor.

*Aim 2 - Ultra-low dissipation networked device: Nanoparticles levitated in vacuum are predicted to have the highest mechanical quality factor of any mechanical object. Such a levitated nanoparticle acts like a little pendulum clock, and in principle if you give it a kick it would take months for it to ring-down. Such behaviour hasn't been realised in optical systems, due to the instability of nanoparticles in optical traps at low pressures, and the fact that the fundamental noise on the light field leads to some additional damping.

The LE system doesn't suffer from these limitations. The potential to provide an electrically networked, ultra-high quality factor oscillator, promises to challenge quartz crystal oscillator technology, which is ubiquitous in communications, navigation, and signal processing, and enable the detection of tiny forces.

*Aim 3 - Ultra-low dissipation quantum device: LEVELECTRO will explore Levitated Cavity Quantum Electromechanics (LCQE) theory, where a levitated charged particle is coupled to quantum microwave cavities. Regular cavity quantum electromechanical systems are at the forefront of quantum technologies, but are limited by a loss of energy (dissipation) from the mechanical element to the environment. LCQE overcomes this problem, promising ultra-low dissipation operation, deep quantum cooling, and the storage of quantum information for tens of seconds.

It is also possible to combine the LCQE system with a levitated cavity quantum optomechanical one, enable the conversion of quantum states of light, to quantum electrical signals. One can foresee the conversion of freely propagating quantum states of light into highly accessible and controllable quantum electrical signals, a much-needed quantum transducer acting as a node in a quantum information network.

LEVELECTRO will realise impact through academic excellence, alignment with national strategy, technological application, and public engagement. This proposal will capitalize on the PIs high standing in the community to rapidly kick-start a successful research group. The PI is committed to ensuring equality in the workplace, as evidenced by his activity on the Juno Committee at UCL, steering the department to Champion status.

**Rapid impact**
Levitated optomechanics is a young, high impact field, with 6 experimental groups generating 19 publications in Science, Nature journals, and Physical Review Letters since 2010. Any experiment working with free/levitated nanoparticles in high vacuum is breaking new ground. As such, LEVELECTRO will be certain to lead to rapid, high impact results, due to the PIs unparalleled experience in the field. The techniques developed in LEVELECTRO will rapidly serve other research groups, through the introduction of an all-electrical control platform.

**Technology**
Proof of principle technological application (TRL2) will be explored with King's IP & Licensing office. The following ideas, for which the PI holds patents, will be explored, by utilizing the NIA and institutional start-up funding: * The combination of optical cavity and ion trap technology, enables mass-and-charge resolved spectrometry. The mass spectrometry industry is relevant to the chemical, biological and medical sciences, and is worth $5.35bn per annum * The control of a rotating nano-object enables sensing of pressure and gas flow, in a range where commercial gauges are inaccurate, with micrometre spatial resolution (note, this application is not included in LEVELECTRO).

LEVELECTRO will explore a new thermodynamic regime, which could lead to new protocols to extract work on the nanoscale, driving nano-machines. This application will be explored with Dr. Janet Anders, a long-time collaborator of the PI.

LEVELECTRO will produce an electrically networked, high-Q oscillator. This is in direct analogy to a quartz crystal oscillator, except with mechanical characteristics (dissipation rates) three order of magnitude better. Further funding for miniaturisation of trapping technology will be explored through a joint proposal with NPL (Sinclair group).

**Long term**
LEVELECTRO will lay foundations for fundamental discoveries, such as a mass limit to quantum phenomena. The PI worked in the world-leading group exploring this topic (Arndt, Vienna), and will continue to collaborate. The control offered by LEVELECTRO will provide new nanoparticle-source technology for matterwave interferometry, and for space based experiments as explored by the MAQRO consortium (Bateman, Swansea. Ulbricht, Southampton).
The long-term goal of the research started in this proposal is the creation of an ultra-low dissipation, long time coherent storage and transduction element in a quantum network. This clearly overlaps with the UKs Quantum Technologies strategy, as explored in greater details in the National Importance section of the Case for Support.

**Public**
This project benefits from the strong public engagement track-record of the PI. LEVELECTRO will be served by the PIs Quantum Workshop (QW) project, a highly visual demonstration to engage with predominantly adult audiences. It covers themes of trapping and quantum technologies, directly relevant to LEVELECTRO. QW will appear at science festivals, public lectures, and in informal spaces such as pubs. The PI has in-depth experience at evaluating public engagement activities to ensure impact, and at training other academics to engage in such activities.
The PI will continue to develop his own personal profile to disseminate the UK quantum technologies strategy, through his public lecture series at the Royal Institution, collaboration with King's Science Gallery, and contacts in media (he acted as scientific advice for 2 BBC series).