Terahertz Quantum Optics

The development of terahertz (THz) technology has brought a new dimension to time-resolved spectroscopy. THz time-domain spectroscopy allows the motion of electrons when interacting with light to be studied. Roland Kersting focuses his research on the quantum dynamical properties of coherent excitations in semiconductors. These dynamics give the most fundamental description of all transient properties of electrons in semiconductors. This understanding of the phase of an electronic excitation offers the potential for the development of entirely new devices, ranging from classical photonics to quantum computers.

Technical Description:
Kersting explains that semiconductor heterostructures are an outstanding material for quantum optical investigations with THz pulses in that their transition frequencies can be tailored by modern semiconductor growth technologies; they are electronically controllable; they can have enormous mobilities; and – perhaps most important – their gigantic dipole moments make for an excellent coupling to THz pulses. This allows Kersting's group to study electronic excitations where the involved quantum dynamics are fully resolved in amplitude and phase. Of particular interest to his research are those dynamics that lead to a loss of electronic coherence, known as decoherence, within the semiconductor. Decoherence is one of the most limiting factors in the development of quantum optical devices.

Another milestone towards THz quantum optics is the demonstration of nonlinear excitation dynamics. Currently, Kersting's group is developing the required technology for such experiments. Future research will focus on the dynamics of absorption saturation, Rabi-flopping and the dynamics that lead to the build-up and decay of so-called dressed states.

Kersting's research targets one of the most exciting challenges in modern physics – the development of a quantum computer. By fulfilling speed, scalability, and parallelizability criterion, THz excitations in semiconductor heterostructures remain one of the most promising opportunities for realizing a quantum computer. Kersting's current research on decoherence and possible quantum operations is a first step towards this major opportunity.

Contact Information:
Roland Kersting
Assistant Professor, Department of Physics
Rensselaer Polytechnic Institute
110 8th Street
Troy, NY 12180-3590

(518) 276-3092