Quantum Spectroscopy

Our group is actively engaged at the interface of quantum optics with physical chemistry. In this research, we manipulate the properties of light at the single photon or few photon level.  By employing “quantum engineered” light for spectroscopy, we aim to harness the remarkable quantum mechanical properties such as entanglement, superposition, and coherence in order to increase the sensitivity and information content of spectroscopy. We are particularly interested in “real world” measurements on complex molecular and nano-materials systems in room temperature liquids, thin films, or crystals.

For example, one of our current projects is focused on two-photon excitation (TPE), a method that is widely used in biological imaging. We are investigating the use of entangled photon pairs (particle pairs created such that the quantum state of each cannot be described independently) as a light source. One provocative question in this field is whether entangled two-photon excitation occurs at many orders of magnitude lower optical power than standard TPE. The physical basis of this quantum enhancement in absorption efficiency is not yet known, but if it can be exploited, entangled TPE and related techniques could enable novel methods for spectroscopic analysis and imaging without sample perturbation.

Our lab has developed specialized experimental facilities for generating and characterizing entangled photon pairs, and for quantifying the interaction of the photons with material by a number of techniques such as photon-counting transmission, photon statistics, or fluorescence. Major challenges in these studies include ensuring that quantum properties of the light are maintained throughout the experimental apparatus, and to discriminate between eTPA and “non-quantum” processes such as scattering. We are pioneering measurement techniques to enable precision measurements of light-matter interactions with defined numbers of photons with single molecules at the nanoscale. Beyond the realm of quantum-enhanced chemical and nano-sensing, these experiments could probe fundamental questions regarding the transition between quantum and classical dynamics.

Through this project, we have established a community of scientists at CU and within the National Institute of Standards and Technology with interest and distinctive expertise in Quantum Biometrology.