Optimizing optical Bragg scattering for single-photon frequency conversion

We develop a systematic theory for optimising single-photon frequency conversion using optical Bragg scattering. The efficiency and phase-matching conditions for the desired Bragg scattering conversion as well as spurious scattering and modulation instability are identified. We find that third-order dispersion can suppress unwanted processes, while dispersion above the fourth order limits the maximum conversion efficiency. We apply the optimisation conditions to frequency conversion in highly nonlinear fiber, silicon nitride waveguides and silicon nanowires. Efficient conversion is confirmed using full numerical simulations. These design rules will assist the development of efficient quantum frequency conversion between multicolour single photon sources for integration in complex quantum networks.Comment: 9 pages, 14 figure

New Deal or "Raw Deal": African Americans and the Pursuit of Citizenship in Indianapolis During FDR's First Term

Indiana University-Purdue University Indianapolis (IUPUI)Race and politics have played an important part in shaping the history of the United States, from the first arrival of African slaves in the early seventeenth century to the election of an African-American president in 2008. The Great Depression and the New Deal represent a period that was no exception to the influence of race and politics. After Franklin Roosevelt succeeded Herbert Hoover to the American presidency, there was much faith and hope expressed on the editorial pages of the Indianapolis Recorder that African Americans would be treated fairly under the New Deal. Hope began to wane when little political patronage was dispensed, in the form of government jobs, once the Democrats took office in 1933. As the first incarnation of the New Deal progressed, African Americans continued to experience prejudice, segregation, unfair wages, and generally a “raw deal.” But what was more, African-American women and men were not given a fair opportunity to ensure for themselves better political, social, and economic standing in the future. This struggle for full-fledged citizenship was further underscored when Congress failed to pass anti-lynching legislation in 1934 and 1935. The New Dealers, Franklin Roosevelt chief among them, did not seize the opportunity presented by the Great Depression to push for civil rights and social justice for African Americans. Their intent was not necessarily malicious. A more nuanced view of the issues shows that political expedience, and a measure of indifference, led the New Dealers to not treat civil rights as the pressing issue that it was. Roosevelt and the New Dealers believed that they faced the potential for significant resistance to their economic recovery program from Southern Democrats on Capitol Hill if they tried to interfere with race relations in the South. This thesis examines the first years of the Roosevelt Administration, roughly 1933 through 1936. This timeframe was carefully chosen because it was a period when the issues surrounding race and racism were brought to the fore. In the initial period of the New Deal we can see how Roosevelt met and failed to meet the expectations of African Americans. The prevailing view among the African American leadership in 1935, argued Harvard Sitkoff, was that the federal government had “betrayed [African Americans] under the New Deal.” Sitkoff referred to these “denunciations of the New Deal by blacks” as commonplace from 1933 to 1935. But beginning with the Second New Deal in the middle 1930s the criticism turned to applause

Vestibular and Attractor Network Basis of the Head Direction Cell Signal in Subcortical Circuits

Accurate navigation depends on a network of neural systems that encode the moment-to-moment changes in an animal\u27s directional orientation and location in space. Within this navigation system are head direction (HD) cells, which fire persistently when an animal\u27s head is pointed in a particular direction (Sharp et al., 2001a; Taube, 2007). HD cells are widely thought to underlie an animal\u27s sense of spatial orientation, and research over the last 25+ years has revealed that this robust spatial signal is widely distributed across subcortical and cortical limbic areas. The purpose of the present review is to summarize some of the recent studies arguing that the origin of the HD signal resides subcortically, specifically within the reciprocal connections of the dorsal tegmental and lateral mammillary nuclei. Furthermore, we review recent work identifying “bursting” cellular activity in the HD cell circuit after lesions of the vestibular system, and relate these observations to the long held view that attractor network mechanisms underlie HD signal generation. Finally, we summarize anatomical and physiological work suggesting that this attractor network architecture may reside within the tegmento-mammillary circuit

Linear Self-Motion Cues Support the Spatial Distribution and Stability of Hippocampal Place Cells

The vestibular system provides a crucial component of place-cell and head-direction cell activity [1-7]. Otolith signals are necessary for head-direction signal stability and associated behavior [8, 9], and the head-direction signal's contribution to parahippocampal spatial representations [10-14] suggests that place cells may also require otolithic information. Here, we demonstrate that self-movement information from the otolith organs is necessary for the development of stable place fields within and across sessions. Place cells in otoconia-deficient tilted mice showed reduced spatial coherence and formed place fields that were located closer to environmental boundaries, relative to those of control mice. These differences reveal an important otolithic contribution to place-cell functioning and provide insight into the cognitive deficits associated with otolith dysfunction

Hybrid photonic circuit for multiplexed heralded single photons

A key resource for quantum optics experiments is an on-demand source of single and multiple photon states at telecommunication wavelengths. This letter presents a heralded single photon source based on a hybrid technology approach, combining high efficiency periodically poled lithium niobate waveguides, low-loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro-optic switches. Hybrid interfacing different platforms is a promising route to exploiting the advantages of existing technology and has permitted the demonstration of the multiplexing of four identical sources of single photons to one output. Since this is an integrated technology, it provides scalability and can immediately leverage any improvements in transmission, detection and photon production efficiencies.Comment: 5 pages, double column, 3 figure

Generation of 3-Dimensional graph state with Josephson charge qubits

On the basis of generations of 1-dimensional and 2-dimensional graph states, we generate a 3-dimensional N3-qubit graph state based on the Josephson charge qubits. Since any two charge qubits can be selectively and effectively coupled by a common inductance, the controlled phase transform between any two-qubit can be performed. Accordingly, we can generate arbitrary multi-qubit graph states corresponding to arbitrary shape graph, which meet the expectations of various quantum information processing schemes. All the devices in the scheme are well within the current technology. It is a simple, scalable and feasible scheme for the generation of various graph states based on the Josephson charge qubits.Comment: 4 pages, 4 figure

Ultra-compact optical auto-correlator based on slow-light enhanced third harmonic generation in a silicon photonic crystal waveguide

The ability to use coherent light for material science and applications is directly linked to our ability to measure short optical pulses. While free-space optical methods are well-established, achieving this on a chip would offer the greatest benefit in footprint, performance, flexibility and cost, and allow the integration with complementary signal processing devices. A key goal is to achieve operation at sub-Watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer, or long tunable delay lines. We report the first device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS compatible device, with the potential to be fully integrated without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as a powerful in-situ diagnostic tool to directly map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals.Comment: 20 pages, 6 figures, 38 reference