The statistical strength of experiments to reject local realism with photon pairs and inefficient detectors

Because of the fundamental importance of Bell's theorem, a loophole-free demonstration of a violation of local realism (LR) is highly desirable. Here, we study violations of LR involving photon pairs. We quantify the experimental evidence against LR by using measures of statistical strength related to the Kullback-Leibler (KL) divergence, as suggested by van Dam et al. [W. van Dam, R. Gill and P. Grunwald, IEEE Trans. Inf. Theory. 51, 2812 (2005)]. Specifically, we analyze a test of LR with entangled states created from two independent polarized photons passing through a polarizing beam splitter. We numerically study the detection efficiency required to achieve a specified statistical strength for the rejection of LR depending on whether photon counters or detectors are used. Based on our results, we find that a test of LR free of the detection loophole requires photon counters with efficiencies of at least 89.71%, or photon detectors with efficiencies of at least 91.11%. For comparison, we also perform this analysis with ideal unbalanced Bell states, which are known to allow rejection of LR with detector efficiencies above 2/3.Comment: 18 pages, 3 figures, minor changes (add more references, replace the old plots, etc.)

Orthotopic xenografts of human melanoma and colonic and ovarian carcinoma in sheep to evaluate radioimmunotherapy.

Extrapolation to humans from experimental radioimmunotherapy in nude mouse xenograft models is confounded by large relative tumour size and small volume of distribution in mice allowing tumour uptake of radiolabelled antibodies unattainable in patients. Our large animal model of human tumours in cyclosporin-immunosuppressed sheep demonstrated tumour uptake of targeted radiolabelled monoclonal antibodies comparable with uptakes reported in clinical trials. Sheep immunosuppression with daily intravenous cyclosporin augmented by oral ketoconazole maintained trough blood levels of cyclosporin within the range 1000-1500 ng ml(-1). Human tumour cells were transplanted orthotopically by inoculation of 10(7) cells: SKMEL melanoma subcutaneously; LS174T and HT29 colon carcinoma into bowel, peritoneum and liver; and JAM ovarian carcinoma into ovary and peritoneum. Tumour xenografts grew at all sites within 3 weeks of inoculation, preserving characteristic morphology without evidence of necrosis or host rejection. Lymphatic metastasis was demonstrated in regional nodes draining xenografts of melanoma and ovarian carcinoma. Colonic LS1 74T xenografts produced mucin and carcinoembryonic antigen (CEA). The anti-CEA IgG1 monoclonal antibody A5B7 was radiolabelled with iodine-131 and administered intravenously to sheep. Peak uptake at 5 days in orthotopic human tumour transplants in gut was 0.027% DI g(-1) (percentage of injected dose per gram) and 0.034% DI g(-1) in hepatic metastases with tumour to blood ratios of 2-2.5. Non-specific tumour uptake in melanoma was 0.003% DI g(-1). Uptake of radiolabelled monoclonal antibody in human tumours in our large animal model is comparable with that observed in patients and may be more realistic than nude mice xenografts for prediction of clinical efficacy of radioimmunotherapy

Imperfect Detectors in Linear Optical Quantum Computers

We discuss the effects of imperfect photon detectors suffering from loss and noise on the reliability of linear optical quantum computers. We show that for a given detector efficiency, there is a maximum achievable success probability, and that increasing the number of ancillary photons and detectors used for one controlled sign flip gate beyond a critical point will decrease the probability that the computer will function correctly. We have also performed simulations of some small logic gates and estimate the efficiency and noise levels required for the linear optical quantum computer to function properly.Comment: 13 pages, 5 figure

Asymptotically optimal data analysis for rejecting local realism

Reliable experimental demonstrations of violations of local realism are highly desirable for fundamental tests of quantum mechanics. One can quantify the violation witnessed by an experiment in terms of a statistical p-value, which can be defined as the maximum probability according to local realism of a violation at least as high as that witnessed. Thus, high violation corresponds to small p-value. We propose a prediction-based-ratio (PBR) analysis protocol whose p-values are valid even if the prepared quantum state varies arbitrarily and local realistic models can depend on previous measurement settings and outcomes. It is therefore not subject to the memory loophole [J. Barrett et al., Phys. Rev. A 66, 042111 (2002)]. If the prepared state does not vary in time, the p-values are asymptotically optimal. For comparison, we consider protocols derived from the number of standard deviations of violation of a Bell inequality and from martingale theory [R. Gill, arXiv:quant-ph/0110137]. We find that the p-values of the former can be too small and are therefore not statistically valid, while those derived from the latter are sub-optimal. PBR p-values do not require a predetermined Bell inequality and can be used to compare results from different tests of local realism independent of experimental details.Comment: 11 pages, 4 figures; Software implementation of the PBR analysis protocol and its user guide attached as ancillary files; minor changes (add the software disclaimer, etc.

901-25 The Paradox of Donor Stimulation of Endothelial-induced Smooth Muscle Growth

Cardiac allograft vasculopathy (CAV) is the major cause of long-term morbidity and mortality in cardiac transplant recipients. It appears to be related to immune damage to the coronary endothelial cells, resulting in intimal proliferation. In order to delineate the mechanisms by which CAY can occur, a co-culture model of human endothelial cells (EC) and smooth muscle cells (SMC) obtained from the donor at the time of organ procurement was utilized. These cells were separated by collagenase digestion, and cultured for four passages. EC and SMC were then grown to confluence in the separate chambers of a co-culture plate separated by a 0.45 micron Millipore filter. Preserved lymphocytes (LYMPH) obtained from the donor and pooled blood lymphocytes from the recipient 3-4 weeks following transplant were added to the EC well so as to cause an immunologic stimulation of the EC. None of the recipients were exposed to monoclonal or polyclonal antibodies to lymphocytes. All cultures and assays were done in triplicate. Results are as follows:Patient#% Increase in donor lymph H3thymidinep ValueDonor 1+510.04Donor 2+450.05Donor 3+1040.05Donor 4+250.01Donor 5-19NSThe donor EC/donor LYMPH co-culture stimulated SMC growth measured by H3thymidine incorporation in 4 of 5 patients. The donor EC/recipient LYMPH co-culture did not result in significant SMC H3thymidine incorporation.ConclusionThese paradoxical findings of a lack in significant SMC proliferation in the recipient stimulated donor cells continue to raise questions in relation to the effects of circulating lymphocytes on the development of cardiac allograft vasculopathy

The film business in the United States and Britain during the 1930s

Film was a most important product in the lives of the people during the 1930s. This paper sets out to analyse the underlying economic arrangements of the film industries of the U.S. and Britain during the decade in producing and diffusing this commodity-type to the population at large. In doing this, the paper finds a highly competitive industry that was built around showing films that audiences wanted to see, irrespective of the extent of vertical integration. It also examines the nature of the inter-relationship between the two industries and finds an asymmetry between the popularity of British films in the American market and that of American films in the British market. Our explanation for this is that the efforts of British firms on the American market were not sufficiently sustained to make a significant impact on American audiences

Bipartite Entanglement in Continuous-Variable Cluster States

We present a study of the entanglement properties of Gaussian cluster states, proposed as a universal resource for continuous-variable quantum computing. A central aim is to compare mathematically-idealized cluster states defined using quadrature eigenstates, which have infinite squeezing and cannot exist in nature, with Gaussian approximations which are experimentally accessible. Adopting widely-used definitions, we first review the key concepts, by analysing a process of teleportation along a continuous-variable quantum wire in the language of matrix product states. Next we consider the bipartite entanglement properties of the wire, providing analytic results. We proceed to grid cluster states, which are universal for the qubit case. To extend our analysis of the bipartite entanglement, we adopt the entropic-entanglement width, a specialized entanglement measure introduced recently by Van den Nest M et al., Phys. Rev. Lett. 97 150504 (2006), adapting their definition to the continuous-variable context. Finally we add the effects of photonic loss, extending our arguments to mixed states. Cumulatively our results point to key differences in the properties of idealized and Gaussian cluster states. Even modest loss rates are found to strongly limit the amount of entanglement. We discuss the implications for the potential of continuous-variable analogues of measurement-based quantum computation.Comment: 22 page

Superradiance and Phase Multistability in Circuit Quantum Electrodynamics

By modeling the coupling of multiple superconducting qubits to a single cavity in the circuit-quantum electrodynamics (QED) framework we find that it should be possible to observe superradiance and phase multistability using currently available technology. Due to the exceptionally large couplings present in circuit-QED we predict that superradiant microwave pulses should be observable with only a very small number of qubits (just three or four), in the presence of energy relaxation and non-uniform qubit-field coupling strengths. This paves the way for circuit-QED implementations of superradiant state readout and decoherence free subspace state encoding in subradiant states. The system considered here also exhibits phase multistability when driven with large field amplitudes, and this effect may have applications for collective qubit readout and for quantum feedback protocols.Comment: Published Versio