The field of quantum information processing (QIP) aims to harness unusual properties of quantum mechanics, such as entanglement and superposition, to achieve an exponential speed-up in certain types of computing tasks. For efficient scalable QIP networks, we require suitable qubits both for long-lived storage, and for point-to-point communications. Atomic systems offer extremely long coherence times (on the order of 1 second), but are not easily transported over long distances; photons are ideal for long-distance communication, but are not easily stored. Fortunately the essential gate operations have been performed with some success on both atomic and photonic systems. The outstanding challenge therefore is to develop robust and efficient means for transferring quantum information between light and matter.
Cavity QED with Arrays of Micro-fabricated Cavities
- Coupling Atoms and Photons
- Optical Microcavities
- Seeing single atoms
- Qubits on demand
- Contacts
- Some Relevant Publications
Roughly speaking, efficient interaction between single photons and atoms relies on focusing a beam of light to an area similar to the photon absorption cross-section of the atom. But this means having a beam size on the order of the square of the wavelength, which is technically challenging to achieve. At the Centre for Cold Matter at Imperial College we are developing a suite of new optical technologies for integration into atom chips - specially designed microfabricated structures - which can be used to cool, trap, and manipulate atoms at temperatures below a millionth of a degree ab
Arguably the most successful method for increasing the interactions between single atoms and photons is to confine them within high-finesse optical microcavities. Here very small mode volumes can be achieved, leading to large single-photon Rabi frequencies, and with relatively long interaction times. At Imperial our resonator design includes a microfabricated spherical mirror, whose small radius of curvature leads to a coherent evolution rate which is ~60 times faster than the spontaneous decay rate of an excited atom in free space, giving rise to a large effective optical depth for even a single atom. Additionally, one mirror of the Fabry-Perot resonator comprises the tip of a single-mode optical waveguide, potentially allowing mode-matched input/output coupling across whole arrays of cavities. By combining our small mode volume with a fast output coupler mirror, we efficiently convert atomic excitations into waveguide-coupled photons without suffering re-absorption.
