Nanophotonic structures can be used to dramatically enhance interactions between light and matter. We describe some of
our recent progress in fabricating optical nanostructures suitable for both classical and quantum information processing.
In particular, we present our progress using nanoimprint lithography, a low cost nanoreplication method, to fabricate low
loss photonic crystals.
Scalable quantum information processing using nitrogen-vacancy (NV) centers in diamond will be difficult without
the ability to couple the centers to optical microcavities and waveguides. Here we present our preliminary
result of coupling a single NV center in a nanoparticle to a silica microdisk at cryogenic temperatures. The
cavity-coupled NV photoluminescence is coupled out of the cavity through a tapered fiber. Although the current
system is limited by the spectral properties of the NV center and the Q of the cavity, efficient particle-cavity
and cavity-waveguide coupling should lead to the realization of a "one-dimensional atom" as needed for CQED,
enable single-shot electron-spin readout, and increase the probability of success in entanglement schemes based
on single-photon detection.
We present two experiments geared toward the realization of a robust and intense source of polarization-entangled
photons. First, we describe a novel source of polarization-entangled pairs that uses periodically-poled potassium
titanyl phosphate (PPKTP) and an interferometer based on polarization beam displacers. The source emits an
intense flux of high-quality single-mode entangled photons and is stable, robust, and easy to align. Second, we
report on sources of correlated photons generated in PPKTP waveguides. Waveguide sources of correlated pairs
have been shown to generate high fluxes of pairs: we theoretically and experimentally investigate spontaneous
parametric down-conversion generation of photon pairs in waveguides at different wavelengths.
We present an experimental approach to study low light level absorption in a tapered optical fiber embedded
in a rubidium atomic vapor medium. Our initial measurements demonstrates the potential of the system to
realize extremely low light level quantum interference effects in the ultra small mode volume of the thin fiber,
which is promising for many practical integrated device applications. The measurement shows saturated
probe absorption using a low optical power of only ten nanowatt. Efforts are underway to use the fiber in a
cloud of trapped rubidium atoms, which will circumvent the transit time limit for demonstrating a low photon
optical switch via quantum interference.
Moore's Law has set great expectations that the performance/price ratio of commercially available semiconductor
devices will continue to improve exponentially at least until the end of the next decade. Although the physics
of nanoscale silicon transistors alone would allow these expectations to be met, the physics of the metal wires
that connect these transistors will soon place stringent limits on the performance of integrated circuits. We
will describe a Si-compatible global interconnect architecture - based on chip-scale optical wavelength division
multiplexing - that could precipitate an "optical Moore's Law" and allow exponential performance gains until
the transistors themselves become the bottleneck. Based on similar fabrication techniques and technologies, we
will also present an approach to an optically-coupled quantum information processor for computation beyond
Moore's Law, encouraging the development of practical applications of quantum information technology for
commercial utilization. We present recent results demonstrating coherent population trapping in single N-V
diamond color centers as an important first step in this direction.
We report on two experiments implementing quantum communications primitives in linear optics systems: a
secure Quantum Random Bit Generator (QRBG) and a multi-qubit gate based on Two-Photon Multiple-Qubit
(TPMQ) quantum logic. In the first we use photons to generate random numbers and introduce and implement
a physics-based estimation of the sequence randomness as opposed to the commonly used statistical tests. This
scheme allows one to detect and neutralize attempts to eavesdrop or influence the random number sequence. We
also demonstrate a C-SWAP gate that can be used to implement quantum signature and fingerprinting protocols.
A source of momentum-entangled photons, remote state preparation, and a C-SWAP gate are the ingredients
used for this proof-of-principle experiment. While this implementation cannot be used in field applications due to the limitations of TPMQ logic, it provides useful insights into this protocol.
We describe how a quantum non-demolition device based on electromagnetically-induced transparency in solidstate atom-like systems could be realized. Such a resource, requiring only weak optical nonlinearities, could potentially enable photonic quantum information processing (QIP) that is much more efficient than QIP based on linear optics alone. As an example, we show how a parity gate could be constructed. A particularly interesting physical system for constructing devices is the nitrogen-vacancy defect in diamond, but the excited-state structure for this system is unclear in the existing literature. We include some of our latest spectroscopic results that indicate that the optical transitions are generally not spin-preserving, even at zero magnetic field, which allows the realization of a Λ-type system.