Quantum Information and Terahertz Technology

Quantum-based communication and measurement systems that use novel quantum states of light are being developed around the world. However, the technologies to generate, manipulate, and detect these states of light are inadequate for the emerging applications. We are developing new light sources, detectors, and measurement techniques to address these needs.

Imaging in the terahertz frequency range enables the detection of concealed weapons and other contraband (e.g., explosives under clothing) without the use of ionizing radiation. Spectroscopy in this frequency range has additional applications in industrial processing and remote identification of chemicals. We are using our unique capabilities in terahertz detectors, optics, metrology methods, and test-beds in these applications.

This project has two main focuses -- the development of optical photon technologies for quantum information science and technology and the development and application of terahertz and millimeter-wave technology and metrology for imaging and spectroscopy.

In the development of single photonics for quantum information science and technology, we work closely with the Nanostructure Fabrication and Metrology Project on the generation of novel non-classical states of light and the detection of single photons. Currently, we are investigating the use of nonlinear fibers and nonlinear crystals as a source of correlated photon pairs or squeezed light. We are also manipulating the squeezed light to make Schroedinger "Cat" states of light. In addition to making non-classical states of light, we build detector systems that are the best in the world at operating at the single photon level. Presently, our project is primarily focused on using two different superconducting detector technologies -- transistion-edge sensors (TES) and superconducting nanowire single photon detectors (SNSPD).

Over the past several years, the Terahertz side of our project has focused on bolometric detection of THz radiation. Our initial work on cryogenic detectors has been extended to antenna-coupled bolometers operating at room temperature. These detectors provide a rugged, low-cost alternative for homeland security applications; e.g., mobile police units or portal scanners in airports. We have established that imaging in the terahertz frequency range has the potential for effectively detecting weapons and contraband concealed by clothing. We have fabricated a focal plane array of antenna-coupled bolometers and demonstrated best-in-class, real-time imaging. We will continue to explore applications of room-temperature (uncooled) and cryogenic antenna-coupled microbolometers. We will perform side-by-side imaging of the same scenes with passive and actively illuminated terahertz camera systems to help settle many outstanding phenomenological questions, such as the capability of terahertz systems to selectively identify specific target materials.

• Demonstrated the highest system detection efficiency for single photons, >95 % at 1550 nm
• First demonstration of time-correlated single photon counting with superconducting single photon detectors
• Developed and demonstrated an ultra-wideband, millimeter-wave/terahertz detector array for use in contraband detection with VTT of Finland
• Developed and characterized a novel, aqueous blackbody calibration (ABC) source for calibrating optical power in the mm-wave to terahertz frequency band