Cavity quantum electrodynamics with a single molecule: Purcell enhancement, strong coupling and single-photon nonlinearity

Abstract

Control of light-matter coupling at the quantum level is an enabling technique for many emerging quantum technologies. This tutorial describes recent advances in achieving efficient coupling of light with a single molecule using an optical Fabry-Perot microcavity. We demonstrate that the efficient cavity-molecule coupling converts the molecule to an effective two-level system. In this regime, a single molecule can act as a nearly perfect reflecting mirror and exhibits optical nonlinearity at the ultimate level of single photons.

Could the Quantum Internet Be Comprised of Molecular Spins with Tunable Optical Interfaces?

“…These forbidden transitions result in low intrinsic optical absorptivity and long optical lifetimes on the order of μs to ms, such that the experimental time scale for single spin measurements would be prohibitively long. However, this practical barrier may be overcome using well-precedented methodologies often applied for spin-bearing defects. ,, Specifically, the rate of emission may be dramatically enhanced by integrating an emitter into a mode-matching optical cavity (Figure c and b). ,, This photonic cavity integration improves the interaction strength of the resonant photon field with the electric dipole of the optical transition, and reduces the optical lifetime through a Purcell enhancement. − As a result, the optical lifetimes of rare-earth ion defects are reduced from milliseconds to microseconds, allowing for measurements at the single spin level. ,,, Moreover, the cavity coupling to the relevant optical transition may increase coherent emission in the ZPL, , as demonstrated with single molecule measurements of PAHs, which would yield more efficient spin-photon entanglement for spin-bearing systems. Naturally, these previous advances suggest that similar approaches would be well-suited for spin-bearing molecular systems.…”

“…181−183 As a result, the optical lifetimes of rare-earth ion defects are reduced from milliseconds to microseconds, allowing for measurements at the single spin level. 58,94,105,184 Moreover, the cavity coupling to the relevant optical transition may increase coherent emission in the ZPL, 50,149 as demonstrated with single molecule measurements of PAHs, which would yield more efficient spin-photon entanglement for spin-bearing systems. Naturally, these previous advances suggest that similar approaches would be well-suited for spin-bearing molecular systems.…”

“…However, even these systems are often still subject to DWFs of ≪100% due to coupling to surrounding ligand or matrix vibrational modes. Thus, while the nested potential energies provide a useful starting point, the DWF may be enhanced through appropriate coupling of the relevant optical transition to a frequency matching mode of an optical cavity (Figure c), as demonstrated with S = 0 polyaromatic hydrocarbon (PAH) systems (see below for further discussion). , …”

Achievements and perspectives of optical fiber Fabry–Perot cavities

“…The high spectral selectivity of FFPCs allows to also control the emission properties of molecules for selected transitions out of complex structure and at the single emitter level [65]. The enhancement of molecule-light field interaction in a FFPC based microcavity has been shown to realize nonlinear wave mixing processes at the single-photon level [45,66].…”

Achievements and Perspectives of Optical Fiber Fabry-Perot Cavities

“…The high spectral selectivity of FFPCs allows to also control the emission properties of molecules for selected transitions out of complex structure and at the single emitter level [60]. The enhancement of molecule-light field interaction in a FFPC based microcavity has been shown to realize nonlinear wave mixing processes at the single photon level [40,61].…”