Ultrafast Quantum Optics

All measurements suffer from noise due to competing processes that cannot easily be filtered or subtracted out. Such background processes obscure the dynamics of interest in spectroscopy and limit the precision of optical phase measurements. It has been shown that using nonclassical light results in improved sensitivity in the presence of noise. In particular, spectroscopy experiments using squeezed light can achieve sensitivities beyond the shot-noise limit. In addition, multiphoton entangled states and entanglement-free implementations of Kitaev’s algorithm in combination with high-flux single photon sources and efficient detectors hold promise for opening up exciting new avenues of research in precision quantum spectroscopy.

We study how correlated photons can separate otherwise unavoidable Feynman diagrams from nonlinear signals, relieving congested molecular spectra of contributions from unwanted pathways. Continuous wave processes in nonlinear crystals are serving as proof-of-principle systems initially, but there may also be interesting implications for time-domain spectroscopy. We also hope to shed light on the advantages and disadvantages of entangled versus non-entangled states in spectroscopy by exploring the differences between applications of NOON states and Heisenberg-limited single photon states.

There is much work to be done in extending quantum information resources into the ultrafast regime. Implementing broadband quantum memories and generating ultrafast paired photons in atomic vapors using four-wave mixing are two directions that are also being explored.

Experiment: 
Selected Publications: 

J. Nunn, K. Reim, K. C. Lee, V. O. Lorenz, B. J. Sussman, I. A. Walmsley, and D. Jaksch, Multimode memories in atomic ensembles, Phys. Rev. Lett. 101, 260502 (2008). [PDF]