An interdisciplinary quantum communications and sensing research effort has been underway at the NASA Glenn Research Center since the summer of 2000. Researchers in the Communications Technology, Instrumentation and Controls, and Propulsion and Turbomachinery Divisions have been working together to study and develop techniques that use the principle of quantum entanglement (QE). This work is supported principally by the Nanotechnology Base R&T program at Glenn. As applied to communications and sensing, QE is an emerging technology that holds promise as a new and innovative way to communicate faster and farther, and to sense, measure, and image environmental properties in ways that are not possible with existing technology.
Quantum entangled photons are "inseparable" as described by a wave function formalism. For two entangled photons, the term "inseparable" means that one cannot describe one photon without completely describing the other. This inseparability gives rise to what appears as "spooky," or nonintuitive, behavior because of the quantum nature of the process. For example, two entangled photons of lower energy can be created simultaneously from a single photon of higher energy in a process called spontaneous parametric down-conversion. Our research is focused on the use of polarization-entangled photons generated by passing a high-energy (blue) photon through a nonlinear beta barium borate crystal to generate two red photons that have orthogonal, but entangled, polarization states. Although the actual polarization state of any one photon is not known until it is measured, the act of measuring the polarization of one photon completely determines the polar ization state of its twin because of entanglement. This unique relationship between the photons provides extra information about the system. For example, entanglement makes it easy to distinguish entangled photons from other photons impinging on a detector. For many other applications, ranging from quantum computation and information to quantum sensing, the entanglement property is critical.
Quantum entanglement setup. Glenn personnel used this setup to verify the presence of entangled photons in the system.
Long description of figure 1.
After the Quantum Communications and Sensing laboratory was completed, our first goal was to verify the presence of entangled photons. The optical setup for this experiment is shown in the preceding photograph. Once verification was complete, a technique known as the "quantum fax" was demonstrated. In this demonstration, an image of a double-slit pattern was "faxed" via a virtual quantum channel from one detector to another. In the demonstration, entangled red photon twins were sent down separate paths. One photon passed through a double slit, and the image of that slit was detected in the other photon (or "faxed") even though it never passed through a slit. Data from the quantum-faxed double-slit are shown in the following graph.
Finally, a comprehensive model of a nanocommunications system using entangled photons was computationally simulated with support from an Undergraduate Student Research Program student. The results showed clearly the feasibility and utility of using quantum-entangled photons for ultra-low-power space communications. High-resolution images can be transmitted over 100 km in free space if entangled photon pairs are used to represent uncoded 8-bit data symbols with less than 27 nW of total photon flux.
Results of the quantum fax experiment. This graph shows an image that was "quantum faxed" using polarization-entangled photons.
Long description of figure 2.
Glenn contacts: Marc Seibert, 216-433-3535, Marc.A.Seibert@nasa.gov; John Lekki, 216-433-5650, John.D.Lekki@nasa.gov; Quang-Viet Nguyen, 216-433-3574, Quang-Viet.Nguyen-1@nasa.gov; Terry Sanders, 216-433-5849, Terry.M.Sanders@nasa.gov; and Kenneth Weiland, 216-433-3843, Kenneth.E.Weiland@nasa.gov
Authors: Dr. Quang-Viet Nguyen and Marc A. Seibert
Headquarters program office: OAT
Programs/Projects: ESE, Space Communications, Propulsion and Power, Propulsion Systems R&T, Nanotechnology Base R&T
Last updated: June 25, 2003
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