Nanophotonics and Quantum Optics

Within the last year, QSR has begun a new basic research program in nanoscale classical and quantum optics for information processing applications, with an emphasis on areas of interest that complement and extend QSR’s existing program in nanoelectronics:

• Experimental quantum information science and technology
• Applications of electromagnetically induced transparency to classical and quantum information processing
• Applications of nanophotonics to classical information processing
• Photonic bandgap nanostructures
• Left-handed (negative index) metamaterials
• Surface-enhanced Raman scattering

Experimental Quantum Information Science and Technology

Quantum Information Science (QIS) is a rapidly emerging discipline with the potential to revolutionize measurement, computation and communication. For example, quantum computation and communication protocols can be devised in which absolute privacy is guaranteed by fundamental laws of physics. Although it is not clear yet that quantum key distribution (QKD) will be the first profitable application of quantum information technology (QIT), it is possible that extensions of QKD (e.g., controlled entanglement swapping), photonic state comparison (for quantum signature verification), and full quantum communication at high data rates will become compelling to financial, medical, and other institutions and their customers. Similarly, quantum metrology and imaging have interest for the nanoscale manufacturing and physical security industries, as these techniques allow tiny phase shifts, displacements, and forces to be accurately measured remotely even when the target is enclosed within an inaccessible or hostile environment. Furthermore, it is already clear that distributed quantum algorithms can efficiently enable solutions to economics problems (e.g., public goods …) that are difficult to treat with conventional mechanisms, but it is not yet known whether other economic procedures — such as resource allocation — have superior quantum solutions.

Our strategy for bootstrapping a QIT industry initially relies on the generation, transmission, processing, and detection of just a few photonic qubits. Our research emphasizes the development of quantum information processing primitives based on nonlinear quantum optics (such as a universal set of optical gates and single-photon detectors) in photonic nanostructures. These primitives would allow us to construct a few-qubit nanoscale quantum optical processor that could be incorporated into existing PCs and communication networks. Just as importantly, the commercial availability in the relatively near future of QIT products would allow scientists, engineers, and customers to begin exploring the viability of practical QIT applications for defense and commercial utilization, and thus nucleate a new industry based on QIT.

Applications of EIT to Classical and Quantum Information Processing

In current implementations of broadband optical information transfer systems, linear optical-electrical-optical converters (OEOCs) unavoidably introduce quantum noise and increase transmitted bit error rates, requiring the use of relatively intense laser carrier fields to improve the signal-to-noise ratio. However, nonlinear integrated optical network elements would allow the OEOCs to be eliminated from the network architecture, dramatically increasing efficiency, SNR, and throughput. In our work, we study aspects of electromagnetically induced transparency and coherent population transfer phenomena and explore how emergent effects at low light levels may be applicable to the generation of a large third-order optical nonlinearity at extremely small distance scales. These effects in themselves are potentially useful for conventional optical information technology, such as optical buffers and delay lines for telecommunications, optical phase shifters for advanced displays, and optical switches that are a factor of at least a million times more efficient than those of current systems. If, in addition, they can be demonstrated to work on non-classical input states of light, then they have the potential to form the basis of components for few-qubit quantum information processing systems, such as single-photon detectors and one-qubit and two-qubit gates.

Applications of Nanophotonics to Classical Information Processing

The optical information technologies industry continues to emphasize the sale and distribution of piecemeal components for infrastructure construction. This approach creates a significant roadblock to wide-scale adoption of optical communication technologies in both the consumer and military markets, because the size and cost of optical components are exorbitant compared to those of the electronic equivalents. This size and cost differential is too great to permit the performance benefits of optical approaches to be fully realized. Therefore, the inevitable thrust of future commercial R&D in this industry will be to drive to ever higher levels of integration, eventually leading to a “Moore’s Law” for optical information technology. Our research focuses on developing practical approaches that allow information processing functions such as buffering and switching to be tuned dynamically at light intensities that are necessarily many orders of magnitude lower than are currently utilized. We are expanding our work in nanoelectronics to find new materials and processing methodologies that can be easily integrated with existing electro-optic components and that will optimize data transfer performance at small scales and low light levels.

Our research in these areas benefits greatly from close multidisciplinary collaborations with other HP organizations and external institutions, including

• Quantum Information Processing Group (HPL Advanced Studies)
• Information Theory Group (HPL Advanced Studies)
• Information Dynamics Lab
• Game Theory and Experimental Economics Program
• Advanced Materials and Processes Lab (HP Technology Development Organization)
• Massachusetts Institute of Technology
• Northwestern University
• University of Oxford

Recent publications and preprints in this new area of investigation include:

1. K.Y. Chen, T. Hogg, and R. G. Beausoleil, “A Quantum Treatment of Public Goods Economics,” Quantum Information Processing 1, 449 (2003).
    
2. R. G. Beausoleil, W. J. Munro, and T. P. Spiller, “Applications of coherent population transfer to quantum information processing (Topical Review),” J. Mod. Opt. 51, 1559 (2004).
    
3. R. G. Beausoleil, W. J. Munro, D. A. Rodrigues, and T. P. Spiller, “Applications of electromagnetically induced transparency to quantum information processing,” J. Mod. Opt. 51, 2441 (2004).
    
4. J. H. Reina, R. G. Beausoleil, T. P. Spiller, and W. J. Munro, “Radiative Corrections and Quantum Gates in Molecular Systems,” Phys. Rev. Lett. 93, 250501 (2004).
    
5. W. J. Munro, K. Nemoto, R. G. Beausoleil, and T. P. Spiller, “High-efficiency quantum nondemolition single-photon-number-resolving detector,” Phys. Rev. A 71, 033819 (2005).
    
6. S. D. Barrett, P. Kok, K. Nemoto, R. G. Beausoleil, W. J. Munro, and T. P. Spiller, “A symmetry analyser for non-destructive Bell state detection using EIT.”
    
7. K.-M. C. Fu, C. Santori, C. Stanley, M. C. Holland, and Y. Yamamoto, “Coherent Population Trapping of Electron Spins in a Semiconductor.”