A. Mink, S. Frankel, and R. Perlner, " Quantum Key Distribution (QKD) and Commodity Security Protocols: Introduction and Integration ", International Journal of network security and its applications, Vol. 1, No. 2, July 2009.

Lijun Ma, Oliver Slattery, Tiejun Chang and Xiao Tang, " Non-degenerated sequential time-bin entanglement generation using periodically poled KTP waveguide ", Optics Express, Vol. 17 Issue 18, pp.15799-15807 (2009).

Lijun Ma, Oliver Slattery and Xiao Tang, " Experimental study of high sensitivity infrared spectrometer with waveguide-based up-conversion detector ", Optics Express Vol. 17, Issue 16, pp. 14395–14404 (2009).

Xiao Tang, Lijun Ma, Oliver Slattery, “Single photon detection and spectral measurement in near infrared region using up-conversion technology” invited talk, presented at LPHYS09, Barcelona, Spain, July 13-17, 2009.

Lijun Ma, Oliver Slattery, Tiejun Chang and Xiao Tang, “Sequential time-bin entanglement generation using periodically poled KTP waveguide”, CLEO/ IQEC (Optical Society of America, Washington, DC, 2009), JWA85.

Xiao Tang, Lijun Ma, Oliver Slattery, “Single photon detection and spectral measurement in near infrared region using up-conversion technology” invited talk, presented at LPHYS09, Barcelona, Spain, July 13-17, 2009.

Burm Baek, Lijun Ma, Alan Mink, Xiao Tang and Sae Woo Nam, " Detector performance in long-distance quantum key distribution using superconducting nanowire single-photon detectors ", Proc. SPIE, Vol. 7320, 73200D (2009).

Oliver Slattery, Alan Mink, and Xiao Tang, " Low noise up-conversion single photon detector and its applications in quantum information systems ", Proc. of SPIE Vol. 7465, 74650W, 2009.

Oliver Slattery, Lijun Ma and Xiao Tang, " Optimization of photon pair generation in dual-element PPKTP waveguide ", Proc. of SPIE Vol. 7465, 74650K, 2009.

Oliver Slattery, Lijun Ma and Xiao Tang, “High-Speed Coincidence Photon Pair Generation by Dual-Element PPKTP Waveguide over GHz repetition rate”, submitted to Frontier in Optics 2009 (the 93rd annual meeting of Optical Society of American, San Jose, October, 2009). WERB review approved.

All Publications.

More Cost Effective QKD System Developed by NIST

Two for One: NIST Design Enables More Cost Effective Quantum Key Distribution

May, 2004.
CONTACT: Ben Stein
(301) 975-3097

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a simpler and potentially lower-cost method for distributing strings of digits, or “keys,” for use in quantum cryptography, the most secure method of transmitting data. The new “quantum key distribution” (QKD) method, outlined in an upcoming paper,* minimizes the required number of detectors, by far the most costly components in quantum cryptography. Although this minimum-detector arrangement cuts transmission rates by half, the NIST system still works at broadband speeds, allowing, for example, real-time quantum encryption and decryption of webcam-quality video streams over an experimental quantum network.

A highly simplified schematic of a recipient's detectors in a quantum cryptography setup. Conventional cryptography setups (left) require at least two detectors, and the most common setup, known as BB84, requires four. By adding an optical component that delays the travel of photons to the detector, the number of required detectors is cut in half. Credit: NIST

In quantum cryptography, a recipient (named Bob) needs to measure a sequence of photons, or particles of light that are transmitted by a sender (named Alice). These photons have information encoded in their polarization, or direction of their electric field. In the most common polarization-based protocol, known as BB84, Bob uses four single-photon detectors, costing approximately $5,000-$20,000 each. One pair of detectors records photons with horizontal and vertical polarization, which could indicate 0 and 1 respectively. The other pair detects photons with “diagonal”, or +/- 45 degree, polarization in which the “northeast” and “northwest” directions alternatively denote 0 and 1.

In the new method, the researchers, led by NIST’s Xiao Tang, designed an optical component to make the diagonally polarized photons rotate by a further 45 degrees and arrive at the same detector but later, and into a separate “time bin”, than the horizontal/vertical polarized ones. Therefore, one pair of detectors can be used to record information from both kinds of polarized photons in succession, reducing the required number of detectors from four to two. In another protocol, called B92, the researchers reduced the required number of detectors from two to one. And in work performed since their new paper, the researchers further developed their approach so that the popular BB84 method now only requires one detector instead of four.

Although in theory quantum cryptography can transmit absolutely secure keys guaranteed by fundamental physical principles (measuring them will disturb their values and make an eavesdropper instantly known), the imperfect properties of photon detectors may undermine system security in practice. For example, photon detectors have an intrinsic problem known as “dead time,” in which a detector is out of commission for a short time after it records a photon, causing it to miss the bit of data that immediately follows; this could result in non-random (and therefore more predictable) bit patterns in which 0s alternate with 1s. Furthermore, inevitable performance differences between detector pairs can also cause them to record less random sequences of digits. The new design avoids these issues and maintains the security of quantum-key-distribution systems in practical applications.