Coherent population trapping of a single nuclear spin under ambient conditions

Coherent control of quantum systems has far-reaching implications in quantum engineering. In this context, coherent population trapping (CPT) involving dark resonances has played a prominent role, leading to a wealth of major applications including laser cooling of atoms and molecules, optical magnetometry, light storage and highly precise atomic clocks. Extending CPT methods to individual solid-state quantum systems has been only achieved in cryogenic environments for electron spin impurities and superconducting circuits. Here, we demonstrate efficient CPT of a single nuclear spin in a room temperature solid. To this end, we make use of a three-level system with a $\Lambda$-configuration in the microwave domain, which consists of nuclear spin states addressed through their hyperfine coupling to the electron spin of a single nitrogen-vacancy defect in diamond. Dark state pumping requires a relaxation mechanism which, in atomic systems, is simply provided by spontaneous emission. In this work, the relaxation process is externally controlled through incoherent optical pumping and separated in time from consecutive coherent microwave excitations of the nuclear spin $\Lambda$-system. Such a pumping scheme with controlled relaxation allows us (i) to monitor the sequential accumulation of population into the dark state and (ii) to reach a new regime of CPT dynamics for which periodic arrays of dark resonances can be observed, owing to multiple constructive interferences. This work offers new prospects for quantum state preparation, information storage in hybrid quantum systems and metrology.Comment: 13 pages including supplementary information, links to figures correcte

Coherent population trapping of a single nuclear spin under ambient conditions

Coherent control of quantum systems has far-reaching implications in quantum engineering. In this context, coherent population trapping (CPT) involving dark resonances has played a prominent role, leading to a wealth of major applications including laser cooling of atoms and molecules, optical magnetometry, light storage and highly precise atomic clocks. Extending CPT methods to individual solid-state quantum systems has been only achieved in cryogenic environments for electron spin impurities and superconducting circuits. Here, we demonstrate efficient CPT of a single nuclear spin in a room temperature solid. To this end, we make use of a three-level system with a $\Lambda$-configuration in the microwave domain, which consists of nuclear spin states addressed through their hyperfine coupling to the electron spin of a single nitrogen-vacancy defect in diamond. Dark state pumping requires a relaxation mechanism which, in atomic systems, is simply provided by spontaneous emission. In this work, the relaxation process is externally controlled through incoherent optical pumping and separated in time from consecutive coherent microwave excitations of the nuclear spin $\Lambda$-system. Such a pumping scheme with controlled relaxation allows us (i) to monitor the sequential accumulation of population into the dark state and (ii) to reach a new regime of CPT dynamics for which periodic arrays of dark resonances can be observed, owing to multiple constructive interferences. This work offers new prospects for quantum state preparation, information storage in hybrid quantum systems and metrology.Comment: 13 pages including supplementary information, links to figures correcte

Experimental and numerical investigations of the optical and thermal aspects of a PCM-glazed unit

This paper reports on the thermal and optical characterisation of PCM (phase change material) RT27 using the T-history method and spectrophotometry principles, respectively, and the experimental and numerical performance evaluation of a PCM-glazed unit. Various relationships describing the variations in the extinction, scattering and absorption coefficients within the phase change region were developed, and were validated in a numerical CFD model. The results show that: (i) during rapid phase changes, the transmittance spectra from the PCM are unstable, while under stable conditions visible transmittance values of 90% and 40% are obtained for the liquid and phases, respectively; (ii) the radiation scattering effects are dominant in the solid phase of the PCM, while radiation absorption dominates in the liquid phase; (iii) the optical/radiation performance of PCM can be successfully modelled using the liquid fraction term as the main variable; (iv) the addition of PCM improves the thermal mass of the unit during phase change, but risks of overheating may be a significant factor after the PCM has melted; (v) although the day-lighting aspects of PCM-glazed units are favourable, the change in appearance as the PCM changes phase may be a limiting factor in PCM-glazed units

A Short Investigation of the Luminescence Properties of Talc

This report presents results of a short study of the thermoluminescence TL properties of talc. Talc is a magnesium silicate mineral utilised widely in industrial and pharmaceutical applications. It occurs in well defined geological situations with several known formation processes, and is extracted by quarrying and mining. The use in foods and dietary supplements is mainly as a filler. The work was initiated to address questions as to the possible impact of talc on application of EN1788 methods to detect irradiated foods. Authentic samples were obtained from extraction and processing facilities in France and Italy. Supplementary samples from Sardinia, China, Mexico and Australia were obtained indirectly. Irradiated pharmaceutical grade talc was obtained from a UK commercial source for comparison. All samples were characterised by TL analysis after initial preparation, and also following irradiation to a 200 Gy dose. The dose response and behaviour under storage at ambient and elevated temperatures and in a light box, were investigated for two samples in detail. Exploratory kinetic analysis was performed to provide first order estimates of trap parameters. All samples of talc exhibited measurable TL response in the 0-500°C region, with at least four recognisable TL peaks present in response to radiation. Sensitivities vary by some 3 or more orders of magnitude from sample to sample, accompanied by less pronounced changes in glow shape following radiation. The dose response increases progressively in the 100-6400 Gy range investigated. At higher dose levels the response is non-linear with the onset of saturation occurring in the kGy region for the majority of signals. Radiation induced signals from all four peaks were stable at ambient temperatures over the duration of the study. Samples stored at 50°C showed some thermal erosion of the low temperature signals. This observation together with analysis of the distribution of natural TL and the kinetic analyses confirms that lower temperature signals have comparable stability with other silicates, and that higher temperature signals are the dominant components of geologically induced signals. The stability requirements to explain natural signals in terms of simple production mechanisms have been defined. Exploratory kinetic analysis confirms that there are multi-trap contributions to the main TL peaks, but provides broad support for a simple explanation of the natural TL. The TL response following high dose irradiation can be distinguished from geological signals by 1-2 orders of magnitude in low temperature peaks. There may be scope for further investigation of phototransfer effects, but these would clearly be overtaken by bleaching in prolonged exposures to light. Thermal processing of pharmaceutical grades of talc reduces residual low temperature signals by some 1-2 orders of magnitude leading to product with negligible low temperature natural signals. TL could in principle be used to verify the effectiveness of such thermal treatment, and potentially to authenticate commercial products. It can also quite clearly be used to identify irradiated talc, providing the amount of prior exposure to light is limited. In samples containing talc in extreme dilution with other unirradiated products, there might be ambiguity in interpretation of glow curves with minor low temperature peaks dominated by high temperature signals. Care would be needed in interpreting EN1788 results of this sort