[show abstract][hide abstract] ABSTRACT: Silicon nanophotonics holds the promise of dramatically advancing the state of the art in computing by enabling parallel architectures
that combine unprecedented performance and ease of use with affordable power consumption. This paper presents a design study
for a many-core architecture called Corona which utilizes dense wavelength division multiplexing (DWDM) for on- and off-chip
communication together with the devices which will be needed to implement such a communication infrastructure.
Applied Physics A 04/2012; 95(4):989-997. · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Optical microcavities and waveguides coupled to diamond are needed to enable efficient communication between quantum systems such as nitrogen-vacancy centers which are known already to have long electron spin coherence lifetimes. This paper describes recent progress in realizing microcavities with low loss and small mode volume in two hybrid systems: silica microdisks coupled to diamond nanoparticles, and gallium phosphide microdisks coupled to single-crystal diamond. A theoretical proposal for a gallium phosphide nanowire photonic crystal cavity coupled to diamond is also discussed. Comparing the two material systems, silica microdisks are easier to fabricate and test. However, at low temperature, nitrogen-vacancy centers in bulk diamond are spectrally more stable, and we expect that in the long term the bulk diamond approach will be better suited for on-chip integration of a photonic network.
[show abstract][hide abstract] ABSTRACT: We report the observation of low-light level optical interactions in a tapered optical nanofiber (TNF) embedded in a hot rubidium vapor. The small optical mode area plays a significant role in the optical properties of the hot vapor Rb-TNF system, allowing nonlinear optical interactions with nW level powers even in the presence of transit-time dephasing rates much larger than the intrinsic linewidth. We demonstrate nonlinear absorption and V-type electromagnetically induced transparency with cw powers below 10 nW, comparable to the best results in any Rb-optical waveguide system. The good performance and flexibility of the Rb-TNF system makes it a very promising candidate for ultralow power resonant nonlinear optical applications.
[show abstract][hide abstract] ABSTRACT: Coupling of the NV-ZPL to a silica microcavity and tapered fiber is demonstrated at cryogenic temperatures. Coupling to a high-Q cavity should enhance the usefulness of the NV-for quantum information applications.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Silicon nanophotonics holds the promise of revolutionizing computing by enabling parallel architectures that combine unprecedented performance and ease of use with affordable power consumption. Here we describe the results of a detailed multiyear design study of dense wavelength division multiplexing (DWDM) on-chip and off-chip interconnects and the device technologies that could improve computing performance by a factor of 20 above industry projections over the next decade.
16th Annual IEEE Symposium on High Performance Interconnects (HOTIC 2008), 26-28 August 2008, Stanford, CA, USA; 01/2008
[show abstract][hide abstract] ABSTRACT: Recently, we verified that spontaneous parametric down conversion (SPDC) is enhanced in a waveguide, in agreement with theory showing an inverse dependence on mode confinement . Here we investigate highly-confined nanophotonic waveguides designed to maximize the SPDC rate. A theory modified to include highly-confined waveguides is used to calculate the spectral width and pair generation rates in a sample system. Pair generation rates exceeding 10(9)/sec/nm/mW are predicted for periodically-poled KTP (PPKTP) nanophotonic waveguides. This results in an enhancement of the downconverted signal power greater than 45x that of low-index-contrast PPKTP waveguides and greater than 6500x that of bulk PPKTP crystals.
[show abstract][hide abstract] ABSTRACT: We present a theoretical and experimental comparison of spontaneous parametric down-conversion in periodically poled waveguides and bulk KTP crystals. We measured a waveguide pair generation rate of 2.9.10(6) pairs/s per mWof pump in a 1-nm band: more than 50 times higher than the bulk crystal generation rate.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Random bit generators (RBGs) are key components of a variety of information processing applications ranging from simulations to cryptography. In particular, cryptographic systems require "strong" RBGs that produce high-entropy bit sequences, but traditional software pseudo-RBGs have very low entropy content and therefore are relatively weak for cryptography. Hardware RBGs yield entropy from chaotic or quantum physical systems and therefore are expected to exhibit high entropy, but in current implementations their exact entropy content is unknown. Here we report a quantum random bit generator (QRBG) that harvests entropy by measuring single-photon and entangled two-photon polarization states. We introduce and implement a quantum tomographic method to measure a lower bound on the "min-entropy" of the system, and we employ this value to distill a truly random bit sequence. This approach is secure: even if an attacker takes control of the source of optical states, a secure random sequence can be distilled.
[show abstract][hide abstract] ABSTRACT: We demonstrate ultra-low light level saturated absorption in a tapered fiber embedded in an atomic vapor. This shows the potential for extremely low light level optical switching and quantum information processing with such a device.
[show abstract][hide abstract] ABSTRACT: Coherent population trapping at zero magnetic field was observed for nitrogen-vacancy centers in diamond under optical excitation. This was measured as a reduction in photoluminescence when the detuning between two excitation lasers matched the 2.88 GHz crystal-field splitting of the color center ground states. This behavior is highly sensitive to strain, which modifies the excited states, and was unexpected following recent experiments demonstrating optical readout of single nitrogen-vacancy electron spins based on cycling transitions. These results demonstrate for the first time that three-level Lambda configurations suitable for proposed quantum information applications can be realized simultaneously for all four orientations of nitrogen-vacancy centers at zero magnetic field.
[show abstract][hide abstract] ABSTRACT: We built an all-fiber random number generator based on polarization-entangled photons that generates high-quality cryptographic random numbers. This setup allows active monitoring of the randomness and independent physics-based testing.
[show abstract][hide abstract] ABSTRACT: Photon pairs generated using spontaneous parametric down- conversion (SPDC) have been a central ingredient for a number of quantum optics experiments ranging from the generation of entanglement to demonstrations of quantum information processing protocols. The flux of pairs generated by SPDC sources has been steadily growing over the years opening the door to practical applications of correlated and entangled photon pairs. SPDC sources based on periodically poled waveguides have shown a great potential to generate large numbers of correlated pairs with a few muW of pump. These works, however, lack a clear explanation of the increased pair rate in waveguides and do not directly compare the waveguide result with bulk. Na"ively, field confinement in waveguides is not expected to enhance pair generation rate, since SPDC is a scattering phenomenon that only involves one pump photon and therefore does not benefit from higher photon densities created by focussing. In this talk we present a theoretical and experimental comparison of spontaneous parametric down-conversion in periodically poled waveguides and bulk KTP crystals. We measured a waveguide pair generation rate of 2.9 .10^6 pairs/s per mW of pump in a 1-nm band: more than 50 times higher than the bulk crystal generation rate. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.NWS07.E3.4
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: All-optical coherent population trapping is possible in nitrogen-vacancy centers in diamond at zero magnetic field. This should allow for simpler implementations of potential devices involving optical manipulation of electron spins.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: 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 Lambda-type system.