A superconducting nanowire single-photon camera with 400,000 pixels.

For the past 50 years, superconducting detectors have offered exceptional sensitivity and speed for detecting faint electromagnetic signals in a wide range of applications. These detectors operate at very low temperatures and generate a minimum of excess noise, making them ideal for testing the non-local nature of reality1,2, investigating dark matter3,4, mapping the early universe5-7 and performing quantum computation8-10 and communication11-14. Despite their appealing properties, however, there are at present no large-scale superconducting cameras-even the largest demonstrations have never exceeded 20,000 pixels15. This is especially true for superconducting nanowire single-photon detectors (SNSPDs)16-18. These detectors have been demonstrated with system detection efficiencies of 98.0% (ref. 19), sub-3-ps timing jitter20, sensitivity from the ultraviolet21 to the mid-infrared22 and microhertz dark-count rates3, but have never achieved an array size larger than a kilopixel23,24. Here we report on the development of a 400,000-pixel SNSPD camera, a factor of 400 improvement over the state of the art. The array spanned an area of 4 × 2.5 mm with 5 × 5-µm resolution, reached unity quantum efficiency at wavelengths of 370 nm and 635 nm, counted at a rate of 1.1 × 105 counts per second (cps) and had a dark-count rate of 1.0 × 10-4 cps per detector (corresponding to 0.13 cps over the whole array). The imaging area contains no ancillary circuitry and the architecture is scalable well beyond the present demonstration, paving the way for large-format superconducting cameras with near-unity detection efficiencies across a wide range of the electromagnetic spectrum.

Single-photon detection in the mid-infrared up to 10 µm wavelength using tungsten silicide superconducting nanowire detectors.

We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 µm. These detectors are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, dark matter searches, and exoplanet spectroscopy.

Demonstration of Einstein-Podolsky-Rosen Steering Using Hybrid Continuous- and Discrete-Variable Entanglement of Light.

Einstein-Podolsky-Rosen steering is known to be a key resource for one-sided device-independent quantum information protocols. Here we demonstrate steering using hybrid entanglement between continuous- and discrete-variable optical qubits. To this end, we report on suitable steering inequalities and detail the implementation and requirements for this demonstration. Steering is experimentally certified by observing a violation by more than 5 standard deviations. Our results illustrate the potential of optical hybrid entanglement for applications in heterogeneous quantum networks that would interconnect disparate physical platforms and encodings.

UV superconducting nanowire single-photon detectors with high efficiency, low noise, and 4 K operating temperature.

For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm. The detectors have active areas up to 56 µm in diameter, 70 - 80% efficiency at temperatures up to 4.2 K, timing resolution down to 60 ps FWHM, blindness to visible and infrared photons, and dark count rates of ∼ 0.25 counts/hr for a 56 µm diameter pixel. These performance metrics make UV SNSPDs ideal for applications in trapped-ion quantum information processing, lidar studies of the upper atmosphere, UV fluorescent-lifetime imaging microscopy, and photon-starved UV astronomy.

Entanglement between more than two hundred macroscopic atomic ensembles in a solid.

There are both fundamental and practical motivations for studying whether quantum entanglement can exist in macroscopic systems. However, multiparty entanglement is generally fragile and difficult to quantify. Dicke states are multiparty entangled states where a single excitation is delocalized over many systems. Building on previous work on quantum memories for photons, we create a Dicke state in a solid by storing a single photon in a crystal that contains many large atomic ensembles with distinct resonance frequencies. The photon is re-emitted at a well-defined time due to an interference effect analogous to multi-slit diffraction. We derive a lower bound for the number of entangled ensembles based on the contrast of the interference and the single-photon character of the input, and we experimentally demonstrate entanglement between over two hundred ensembles, each containing a billion atoms. We also illustrate the fact that each individual ensemble contains further entanglement.Multipartite entanglement is of both fundamental and practical interest, but is notoriously difficult to witness and characterise. Here, Zarkeshian et al. demonstrate multipartite entanglement in an atomic frequency comb storing a single photon in a Dicke state spread over a macroscopic ensemble.

Heralded Single Photons Based on Spectral Multiplexing and Feed-Forward Control.

We propose and experimentally demonstrate a novel approach to a heralded single-photon source based on spectral multiplexing (SMUX) and feed-forward-based spectral manipulation of photons created by means of spontaneous parametric down-conversion in a periodically poled LiNbO_{3} crystal. As a proof of principle, we show that our three-mode SMUX increases the heralded single-photon rate compared to that of the individual modes without compromising the quality of the emitted single photons. We project that by adding further modes, our approach can lead to a deterministic single-photon source.

Demonstration of Einstein-Podolsky-Rosen Steering Using Single-Photon Path Entanglement and Displacement-Based Detection.

We demonstrate the violation of an Einstein-Podolsky-Rosen steering inequality developed for single-photon path entanglement with displacement-based detection. We use a high-rate source of heralded single-photon path-entangled states, combined with high-efficiency superconducting-based detectors, in a scheme that is free of any postselection and thus immune to the detection loophole. This result conclusively demonstrates single-photon entanglement in a one-sided device-independent scenario, and opens the way towards implementations of device-independent quantum technologies within the paradigm of path entanglement.

Optical Synthesis of Large-Amplitude Squeezed Coherent-State Superpositions with Minimal Resources.

We propose and experimentally realize a novel versatile protocol that allows the quantum state engineering of heralded optical coherent-state superpositions. This scheme relies on a two-mode squeezed state, linear mixing, and a n-photon detection. It is optimally using expensive non-Gaussian resources to build up only the key non-Gaussian part of the targeted state. In the experimental case of a two-photon detection based on high-efficiency superconducting nanowire single-photon detectors, the freely propagating state exhibits a 67% fidelity with a squeezed even coherent-state superposition with a size |α|(2)=3. The demonstrated procedure and the achieved rate will facilitate the use of such superpositions in subsequent protocols, including fundamental tests and optical hybrid quantum information implementations.

High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films.

We report on MoSi SNSPDs which achieved high system detection efficiency (87.1 ± 0.5% at 1542 nm) at 0.7 K and we demonstrate that these detectors can also be operated with saturated internal efficiency at a temperature of 2.3 K in a Gifford-McMahon cryocooler. We measured a minimum system jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.3 ± 0.1%. The performance of MoSi SNSPDs at 2.3 K is similar to the performance of WSi SNSPDs at < 1 K. The higher operating temperature of MoSi SNSPDs makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation.

Efficient Bell state analyzer for time-bin qubits with fast-recovery WSi superconducting single photon detectors.

We experimentally demonstrate a high-efficiency Bell state measurement for time-bin qubits that employs two superconducting nanowire single-photon detectors with short dead-times, allowing projections onto two Bell states, |ψ⁻〉 and |ψ⁺〉. Compared to previous implementations for time-bin qubits, this yields an increase in the efficiency of Bell state analysis by a factor of thirty.

Thermally induced parametric instability in a back-action evading measurement of a micromechanical quadrature near the zero-point level.

We report the results of back-action evading experiments utilizing a tightly coupled electro-mechanical system formed by a radio frequency micromechanical resonator parametrically coupled to a NbTiN superconducting microwave resonator. Due to excess dissipation in the microwave resonator, we observe a parametric instability induced by a thermal shift of the mechanical resonance frequency. In light of these measurements, we discuss the constraints on microwave dissipation needed to perform BAE measurements far below the zero-point level.

Synchronous basal cell carcinoma and meningioma following cranial irradiation for a pilocytic astrocytoma.

We report a case of synchronous radiation-induced meningioma and basal cell carcinoma in a 48-year-old man who presented to the plastic surgeons with a fixed scalp lesion sited over a craniotomy scar. Synchronous radiation-induced tumours are a rare occurrence.

Efficacy and safety of the endothelin, receptor antagonist TAK-044 in treating subarachnoid hemorrhage: a report by the Steering Committee on behalf of the UK/Netherlands/Eire TAK-044 Subarachnoid Haemorrhage Study Group.

OBJECT: Delayed cerebral ischemia remains an important cause of death and disability in patients who have suffered subarachnoid hemorrhage (SAH). Endothelin (ET) has a potent contractile effect on cerebral arteries and arterioles and has been implicated in vasospasm. The authors administered ET(A/B) receptor antagonist (TAK-044) to patients suffering from aneurysmal SAH. They then assessed whether this agent reduced the occurrence of delayed cerebral ischemic events and examined its safety profile in this group of patients. METHODS: Four hundred twenty patients who had suffered an SAH were recruited into a multicenter, randomized, double-blind, placebo-controlled, parallel-group phase II trial. The primary end point was whether a delayed ischemic event occurred within 3 months after the first dose of the study drug and the secondary end points included determining whether a delayed ischemic event occurred by 10 days after the first dose of the study drug, whether a new cerebral infarct was demonstrated on a computerized tomography scan or at postmortem examination by 3 months after administration of the initial dose, the patient's Glasgow Outcome Scale scores at 3 months after the initial dose, and adverse events. There was a lower incidence of delayed ischemic events at 3 months in the TAK-044-treated group: 29.5% compared with 36.6% in a group of patients receiving placebo. The estimated relative risk was 0.8 with a 95% confidence interval of 0.61 to 1.06. There were no significant differences in the secondary end points, including clinical outcomes in the placebo-treated and TAK-044-treated groups. CONCLUSIONS: The TAK-044 was well tolerated by patients who had suffered an SAH, even though hypotension and headache--side effects compatible with the drug's vasodilatory properties--occurred. It would be valuable to proceed to a fully powered phase III trial of an ET receptor antagonist in treating aneurysmal SAH.

Spontaneous chronic and subacute subdural haematoma in young adults.

Spontaneous subacute and chronic haematoma in young adults is rare. It has not been previously reported in this age group. We present three cases of chronic and subacute subdural haematoma in young adults, in one of whom the diagnosis was certainly delayed. All three patients underwent burrhole evacuation and made a full neurological recovery. A cause for the haematoma was never established. The literature on the subject, which is scanty, is reviewed and the condition is briefly discussed. The aetiology remains obscure.

Head injuries in four British neurosurgical centres.

An issue in the design of trials in traumatic brain injury is whether variation amongst centres in 'conventional' management could mask the impact of a powerful new pharmacological agent. We report the results of an observational study of 988 patients admitted to one of four British neurosurgical units between 1986 and 1988 within 3 days of a severe head injury. The centres fell into two pairs on the basis of the 'intensity' of management. In Edinburgh and Southampton, more frequent use of intracranial pressure monitoring, ventilation and osmotic diuretics was made than in Glasgow and Liverpool. The odds ratio for an independent outcome at 6 months in Edinburgh or Southampton, relative to Glasgow or Liverpool, controlling for case mix, was 1.43 (95% CI, 1.03-1.98, p = 0.033). Thus, there is weak evidence of an association between the approach to management and clinical outcome at 6 months.

Local delivery of cytokines by retrovirally transduced antigen-specific TCR+ hybridoma cells in experimental autoimmune encephalomyelitis.

Autoimmune diseases in humans represent an immune attack on self tissue. Current therapies for almost all autoimmune diseases utilize potent and nonspecific immunosuppressive regimens. These therapies are complicated by their side effects and also place the patient at increased risk for opportunistic infections and malignancies. Our current understanding of immune mechanisms underlying autoimmune diseases remains limited. Ongoing studies include identifying genes that predispose an individual to developing autoimmunity, identification of autoantigens that trigger or perpetuate autoimmunity, and studies of immune cell interactions that lead to immune response. Although it may be many years before a full understanding of autoimmunity is obtained, treatment in animal models of autoimmune disease and some human clinical trials have begun to study alternative treatment approaches to therapy of autoimmune disease. Future therapies for autoimmune diseases should target the inappropriate autoimmune response. This article will describe the use of gene therapy in the treatment of autoimmune disease. We believe that autoimmunity can be ameliorated by delivering trans-acting immunoregulatory molecules by retrovirally transduced autoantigen specific T cells that home to lesions of autoimmunity. Until recently, there has not been a practical alternative to systemic delivery of immunoregulatory molecules, however systemic delivery suffers from toxic side effects and dangerous global immunosuppression. In order to study immune regulation using retroviral transduction for local delivery of immunoregulatory products, we used myelin basic protein (MBP) reactive T cell hybridomas in the murine model of multiple sclerosis (MS), experimental allergic encephalomyelitis (EAE). In this report, we show that MBP reactive T cell hybridomas transduced to express IL-4 or TNF, ameliorated or exacerbated disease, respectively. Additionally, the effects of these cells were dependent on T cell receptor (TCR) expression, indicating that the effects were due to homing of the T cells and the local delivery of cytokines. We believe that gene therapy, allowing local delivery of immunoregulatory proteins by autoantigen specific T cells, represents an interesting potential therapy for autoimmune disease.

A peptide mimic of a protective epitope of respiratory syncytial virus selected from a combinatorial library induces virus-neutralizing antibodies and reduces viral load in vivo.

Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and pneumonia in infants and young children worldwide. As yet, there is no effective vaccine against RSV infection, and previous attempts to develop a formalin-inactivated vaccine resulted in exacerbated disease in recipients subsequently exposed to the virus. In the work described here, a combinatorial solid-phase peptide library was screened with a protective monoclonal antibody (MAb 19) to identify peptide mimics (mimotopes) of a conserved and conformationally-determined epitope of RSV fusion (F) protein. Two sequences identified (S1 [HWYISKPQ] and S2 [HWYDAEVL]) reacted specifically with MAb 19 when they were presented as solid-phase peptides. Furthermore, after amino acid substitution analyses, three sequences derived from S1 (S1S [HWSISKPQ], S1K [KWYISKPQ], and S1P [HPYISKPQ]), presented as multiple antigen peptides (MAPs), also showed strong reactivity with MAb 19. The affinity constants of the binding of MAb 19, determined by surface plasmon resonance analyses, were 1.19 x 10(9) and 4.93 x 10(9) M(-1) for S1 and S1S, respectively. Immunization of BALB/c mice with these mimotopes, presented as MAPs, resulted in the induction of anti-peptide antibodies that inhibited the binding of MAb 19 to RSV and neutralized viral infection in vitro, with titers equivalent to those in sera from RSV-infected animals. Following RSV challenge of S1S mimotope-immunized mice, a 98.7% reduction in the titer of virus in the lungs was observed. Furthermore, there was a greatly reduced cell infiltration in the lungs of immunized mice compared to that in controls. These results indicate the potential of peptide mimotopes to protect against RSV infection without exacerbating pulmonary pathology.

How many higher neurosurgical trainees shall we train in the British Isles?

In the British Isles there are a small number of neurosurgeons. The number of career trainees has been rigorously controlled over the years, such that there is a sufficient number to satisfy the number of new consultants required as the result of retirement and the creation of new posts. The number of career trainees posts is 89 but the current calculated requirement is for 112 career trainees. In addition overseas trainees come to the British Isles, usually for a specific part of their training.