Demonstrating sub-3 ps temporal resolution in a superconducting nanowire single-photon detector

Improving the temporal resolution of single photon detectors has an impact on many applications, such as increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the highest efficiency time-resolving single-photon counting detectors available in the near infrared. As the detection mechanism in SNSPDs occurs on picosecond time scales, SNSPDs have been demonstrated with exquisite temporal resolution below 15 ps. We reduce this value to 2.7$\pm$0.2 ps at 400 nm and 4.6$\pm$0.2 ps at 1550 nm, using a specialized niobium nitride (NbN) SNSPD. The observed photon-energy dependence of the temporal resolution and detection latency suggests that intrinsic effects make a significant contribution.Comment: 25 pages, 9 figure

Telecom networking with a diamond quantum memory

Practical quantum networks require interfacing quantum memories with existing channels and systems that operate in the telecom band. Here we demonstrate low-noise, bidirectional quantum frequency conversion that enables a solid-state quantum memory to directly interface with telecom-band systems. In particular, we demonstrate conversion of visible-band single photons emitted from a silicon-vacancy (SiV) center in diamond to the telecom O-band, maintaining low noise ($g^2(0)<0.1$) and high indistinguishability ($V=89\pm8\%$). We further demonstrate the utility of this system for quantum networking by converting telecom-band time-bin pulses, sent across a lossy and noisy 50 km deployed fiber link, to the visible band and mapping their quantum states onto a diamond quantum memory with fidelity $\mathcal{F}=87\pm 2.5 \%$. These results demonstrate the viability of SiV quantum memories integrated with telecom-band systems for scalable quantum networking applications.Comment: 9 pages, 5 figures + Supplemental Material

Development of a Boston-area 50-km fiber quantum network testbed

Distributing quantum information between remote systems will necessitate the integration of emerging quantum components with existing communication infrastructure. This requires understanding the channel-induced degradations of the transmitted quantum signals, beyond the typical characterization methods for classical communication systems. Here we report on a comprehensive characterization of a Boston-Area Quantum Network (BARQNET) telecom fiber testbed, measuring the time-of-flight, polarization, and phase noise imparted on transmitted signals. We further design and demonstrate a compensation system that is both resilient to these noise sources and compatible with integration of emerging quantum memory components on the deployed link. These results have utility for future work on the BARQNET as well as other quantum network testbeds in development, enabling near-term quantum networking demonstrations and informing what areas of technology development will be most impactful in advancing future system capabilities.Comment: 9 pages, 5 figures + Supplemental Material

Education for sustainable development in higher education: evaluating coherence between theory and praxis

Universities are an important part of the process of change taking place in society. However, this is often overshadowed by these institutions giving priority to technocratic models in the relationship between science and society. In this context, according to Habermas, theories can serve to clarify practical questions and guide praxis into the right actions (social emancipation and rational autonomy). Habermas introduces the need to evaluate the particular contexts in which scientific arguments are made and assessed. The aim of this study was to develop a set of assessment criteria for education for sustainable development in higher education curricula. These were developed in line with Habermas by introducing further adaptions within the context of education for sustainable development. These criteria were tested in a blended learning master’s programme in Environmental Citizenship and Participation at the Universidade Aberta, Portugal. The following research tools were used as follows: (i) a questionnaire survey to the graduates; (ii) content analysis applied to the information guide and to the abstracts of the dissertations that were produced. The case study revealed that an absence of theoretical frameworks could lead to inconsistencies between theory and praxis. Improvements to curricula are then drawn from this study

Optical coherence of diamond nitrogen-vacancy centers formed by ion implantation and annealing

© 2019 American Physical Society. The advancement of quantum optical science and technology with solid-state emitters such as nitrogen-vacancy (NV) centers in diamond critically relies on the coherence of the emitters' optical transitions. A widely employed strategy to create NV centers at precisely controlled locations is nitrogen ion implantation followed by a high-temperature annealing process. We report on experimental data directly correlating the NV center optical coherence to the origin of the nitrogen atom. These studies reveal low-strain, narrow-optical-linewidth (1 GHz) and higher strain. The data show that the poor optical coherence of the NV centers formed from implanted nitrogen is not due to an intrinsic effect related to the diamond or isotope. These results have immediate implications for the positioning accuracy of current NV center creation protocols and point to the need to further investigate the influence of lattice damage on the coherence of NV centers from implanted ions