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2004 World Technology Awards Winners & Finalists

Sae Woo Nam

Please describe the work that you are doing that you consider to be the most innovative and of the greatest likely long-term significance.

Fast, accurate, and secure communication is one of the biggest challenges in information technology. For the past twenty, research and development in the new area of quantum information science and technology has been steadily growing.. Recently, the ultimate in secure communication systems (based on quantum cryptography or quantum key distribution) has moved from academic and government research labs into commercially available systems. The security of these systems relies theoretically on our belief in quantum physics and practically on the encoding of information onto single photons. In the optimum configurations, the communications is provably secure not only during the transmission, but also at any future point in time. Unfortunately, verification and calibration of these systems will remain impossible until the number of photons in a pulse of light can be accurately measured. Based on very recent laboratory results in my lab at NIST, we have been able to demonstrate a detector with this capability of counting the number of photons, the smallest, indivisible unit for light, in a faint pulse of light. This would be analogous to counting the number of electrons in a pulse of electrical current. We have demonstrated this advanced detector systems for use not only at the three telecommunication wavelengths (850 nm, 1310 nm, 1550 nm) but also at optically visible wavelengths. Dr. Duncan Miller of BBN Technologies has said of our NIST work, “Your work forms a key milestone … since the security of quantum cryptography ultimately rests upon the accurate production of single photons, new calibration and detection instruments … [which] are of crucial importance to the field ... We know exactly how we will employ [these instruments] … and we very much look forward to collaborating with NIST.” In addition to quantum cryptography, our detector technology which exploits the properties of superconducting materials can be used by a variety of scientists and engineers from those who are evaluating advanced light sources for communication links or teleporting quantum states to those who are testing the fundamental assumption of quantum mechanics, examining fluorescence signals from biological material, or looking at the faintest stars to find other “class M” planets. As we continue to improve the performance of superconducting detectors, it is not difficult to imagine even more elaborate applications and impact. Our team at NIST is leading an effort to make extremely high quantum efficiency (the probability of a detecting a single photon is nearly 100%) photon detectors. The high efficiency combined with the photon counting metrology could enable a new paradigm in computing known as a quantum computer. With such a computer, cryptography implemented as we know it now would be rendered useless. Only communication encoded with quantum cryptography would be secure. With more improvements in speed that have been demonstrated in prototype superconducting detector systems, it’s not difficult to imagine the ultimate in low power optical communication links. For example, as NASA pushes space exploration to farther and farther distances with space probes, detectors that are able to count the fundamental unit of light, a photon, will be needed at the receiving station on the ground. My group at NIST is excited to be pursuing superconducting detector technologies that are approaching the ultimate limit in performance. I believe that our recent work (as well as others) in the area of superconducting detectors has occurred at a very unique time. Because of the unprecedented sensitivity of these detectors, new techniques in classical communications are now possible. In addition, these detectors are beginning to play an important role in the evolution quantum information science and technology that is beginning to change they way we think about, represent, manipulate, and measure information now.

Brief Biography

Dr. Sae Woo Nam attended the Massachusetts Institute of Technology, where he received a degree in Physics and a degree in Electrical Engineering in 1991. He did his graduate studies at Stanford University where he received two degrees in physics: M.S. (1998) and Ph.D. (1998). His thesis research focused on the development of large cryogenic detectors for direct detection of dark matter particles using superconducting transition-edge sensors for the Cryogenic Dark Matter Search experiment (CDMS). Following his degree, he was awarded an NRC Postdoctoral Fellowship at NIST to continue work on advanced applications of superconducting transition-edge sensor (TES) based detectors. The applications have included development of a high-energy resolution x-ray detector system which is being commercialized and the development of an advanced detector readout scheme that will be used in next generation ground-based sub-mm telescopes (e.g. SCUBA2). He was hired full time at NIST in 2001 to continue this and other advanced metrology work. He has been involved (both at Stanford and NIST) with the first demonstration of using TES sensors to directly detect optical photons, the first use of a TES optical photon sensor for astronomical observations, and the first use of TES detectors for photon number resolving detection in weak pulses of light at telecommunication and optical wavelengths. Recently, he has participated in the development of a superconducting qubit based on large area Josephson junctions.

Dr. Sae Woo Nam received a 2002 PECASE (Presidential Early Career Award for Scientists and Engineers) for work on advanced photon detectors and contributions to the field of primary thermometry using Johnson noise. Dr. Nam was also recently recognized in 2003 as one of the “Brilliant 10” by Popular Science magazine.