Solid State Superatoms

The modern digital world relies on classical two-level systems - binary bits. A major theme of current physics research is the development of their quantum equivalent "qubits" - isolated two-level quantum systems, for applications in computing, sensing, measurement and communication. A logical quantum bit may be encoded using the physical states of an ensemble of many individual atoms. A powerful way to carry out such a collective encoding is to exploit highly excited electronic states, known as Rydberg states that have strong long-range interactions with neighbouring atoms. So far, this method has been demonstrated in a laser-cooled atomic gas, but not in the solid state.

We propose to use atom-like electronic states known as excitons, in a semiconducting signal. Excitons couple to light and can be excited to a Rydberg state, where their wavefunction can encapsulate billions of lattice sites. Using methods from solid state physics (strain engineering) and atomic physics (microwave control), we aim to isolate collective solid state two-level systems (superatoms), and prove their existence using the quantum properties of the light they emit. Finally we plan to exploit the translational symmetry of the bulk crystal environment to create tailored arrays of superatoms.

Short term: The primary beneficiary of the proposed work is the UK Quantum technology community (scientists, engineers and companies), in the following ways:
-People: The project will directly train two PDRAs in the cutting-edge skills needed in the quantum technology arena, and provide a training opportunity for at least two graduate students, as well as undergraduates.
-Knowledge: We open up a new research direction in the solid state that exploits atom-like highly excited states, with applications that include quantum optics and quantum interfaces. The proposal combines methods from solid state and atomic physics, with impact in both. We plan to use this project link these communities more closely.

Medium and long term: Economic impact could result in the medium to long term, through applications of the proposed research to sources of non-classical light and interfaces to superconducting quantum circuits such as those used in the first commercial quantum computer (D-Wave).