Gregory S. Kanter

Quantum-noise randomized data encryption for wavelength-division-multiplexed fiber-optic networks

We demonstrate high-rate randomized data-encryption through optical fibers using the inherent quantum-measurement noise of coherent states of light. Specifically, we demonstrate 650 Mbit/s data encryption through a 10 Gbit/s data-bearing, in-line amplified 200-km-long line. In our protocol, legitimate users (who share a short secret key) communicate using an M-ry signal set while an attacker (who does not share the secret key) is forced to contend with the fundamental and irreducible quantum-measurement noise of coherent states. Implementations of our protocol using both polarization-encoded signal sets as well as polarization-insensitive phase-keyed signal sets are experimentally and theoretically evaluated. Different from the performance criteria for the cryptographic objective of key generation (quantum key-generation), one possible set of performance criteria for the cryptographic objective of data encryption is established and carefully considered.

Wavelength-selective pulsed all-optical switching based on cascaded second-order nonlinearity in a periodically poled lithium-niobate waveguide

We report all-optical switching in a time and wavelength window based on cascaded sum- and difference-frequency generation in a periodically poled lithium-niobate waveguide. More than 50% switching of a 5-ps pulse is observed with a gate-pulse peak power of 6.6 W.

Quantum noise protected data encryption in a WDM network

We demonstrate fully streaming optical data encryption over a 250-km-long fiber-optic wavelength-division-multiplexing (WDM) line at OC-12 data rate. Our scheme, based on the fundamental and irreducible quantum noise of laser light, allows for optical amplification and is shown to be compatible with todays high-speed WDM telecommunications infrastructure.

Noise-enhanced encryption for physical layer security in an OFDM radio

We adapt a physical-layer modulation scheme previously used for enhancing security in the optical domain to an OFDM radio link. The method relies on manipulating the signal constellation according to a cryptographic pseudo-random number generator and adding a small amount of truly random noise at the transmitter. We test the ultra-secure format by generating modified 802.11a packets offline and transmitting them over-the-air using a radio board designed for software defined radio applications. Our initial test system uses an underlying QPSK data format with a 12Mb/s burst-mode data rate. No performance penalty was observed by adding the noise-enhanced encryption function.

Practical physical-layer encryption: The marriage of optical noise with traditional cryptography

We describe an emerging method of encryption suitable for high-speed optical communication networks. This encryption protocol combines traditional electronic cryptographic algorithms with the physical effect of optical noise of quantum origin to create a highly secure method of secret communications. The resulting optical signal is compatible with todays high speed fiber optic infrastructure including optical amplification and add/drop multiplexing. Systems implementing this protocol can be constructed with common commercially available components. We describe experimental results obtained with a 2.5 Gb/s system. The encrypted signal is shown to travel error-free through >500 km of optical fiber. Simulations show that reaches and data rates consistent with modern long haul optical networks are attainable.

Squeezing in a LiNbO3 integrated optical waveguide circuit

We report on traveling-wave quadrature squeezing generated in an integrated optical circuit fabricated with periodicallypoled lithium niobate waveguides. The device integrates a secondharmonic-generation stage, waveguide couplers, spatial mode filters, and a degenerate-optical-parametric-amplification stage. The integrationpromises to create a low power, compact, and simple source of wideband squeezed light. -1 dB of squeezing is directly measured using 20 ps pulses with peak powers near 6W.

Characterization of dynamic optical nonlinearities by continuous time-resolved Z-scan

Dynamic optical nonlinearities are investigated with a dual-beam (pulsed-pump, cw probe) Z-scan technique. Monitoring of probe transmission after strong pump excitation permits determination of time-varying parameters such as nonlinear refraction n(I, t) and absorption alpha(I, t). Continuous time resolution provides an efficient means of measuring and distinguishing fast and slow nonlinear mechanisms such as electronic, free-carrier, and thermal effects observed in semiconductors. We demonstrate this technique in CdTe and measure bound-electronic refraction; two-photon absorption; free-carrier refraction, absorption, and diffusion; thermal refraction and temperature changes; and related time constants.

Robust Multiwavelength All-Fiber Source of Polarization-Entangled Photons With Built-In Analyzer Alignment Signal

We describe an all-fiber source of polarization-entangled photons, which is designed to be simple to manufacture and structurally robust. The source includes an alignment signal that allows for straightforward alignment of the measurement axes of the subsequent polarization analyzers. High-quality entangled light is generated and measured at multiple wavelength channels within the C-band.

Multidimensional mode-separable frequency conversion for high-speed quantum communication

Quantum frequency conversion (QFC) of photonic signals preserves quantum information while simultaneously changing the signal wavelength. A common application of QFC is to translate the wavelength of a signal compatible with the current fiber-optic infrastructure to a shorter wavelength more compatible with high quality single-photon detectors and optical memories. Recent work has investigated the use of QFC to manipulate and measure specific temporal modes (TMs) through tailoring of the pump pulses. Such a scheme holds promise for multidimensional quantum state manipulation that is both low loss and re-programmable on a fast time scale. We demonstrate the first QFC temporal mode sorting system in a four-dimensional Hilbert space, achieving a conversion efficiency and mode separability as high as 92% and 0.84, respectively. A 20-GHz pulse train is projected onto 6 different TMs, including superposition states, and mode separability with weak coherent signals is verified via photon counting. Such ultrafast high-dimensional photonic signals could enable long-distance quantum communication with high rates.

Quantum optical arbitrary waveform manipulation and measurement in real time

We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing.