A theoretical proposal for testing Bell's inequality in mesoscopic systems is presented. We show that the entanglement of two electron spins can be detected in the spin filter effect in the mesoscopic semiconductor / ferromagnetic semiconductor / semiconductor junction. The current-current correlation function is calculated by use of the quantum scattering theory and we compare it with the local hidden variable theory. We also discuss the influence of an imperfect spin filter and derive the condition to see the violation of Bell's inequality experimentally.Entanglement, or quantum nonlocality between quantum systems, is a remarkable feature of quantum mechanics which gives rise to striking phenomena such as the violation of Bell's inequality.1,2 Bell's inequality has already been tested experimentally with photons, i.e., massless particles.3-5 To date, however, none of experiment have been seen for massive particles such as electrons. On the other hand, the semiconductor micro-fabrication techniques have allowed us to test the foundations of quantum mechanics in mesoscopic systems. Recent experimental studies include the fermionic two-particle interferometry (electron anti-bunching experiment)6 and the Hanbury Brown and Twiss experiment 7,8 in semiconductor micro-structures. However these phenomena are not based on the nature of entangled particles. Although many methods to generate a spin-entangled electron pair in mesoscopic devices have been proposed, 9-13 there exists no clear theoretical proposal for the test of the violation of Bell's inequality for spin-entangled electrons in these systems.In this letter we shall show that mesoscopic semiconductor / ferromagnetic semiconductor / semiconductor (S/FS/S) systems provide a possibility to test Bell's inequality. It was shown that the spin decoherence time for electrons in semiconductors is very long, i.e., on the order of microseconds.14 Therefore, the electron spin in these systems becomes a good candidate for investigating Bell's inequality in a solid state environment. The scheme we proposed here consists of an entangler and the S/FS/S junction which act as a spin-polarized beam splitter (SPBS). We shall show how to generate, manipulate and detect spin-entangled states experimentally. For this purpose, we calculate the currentcurrent correlation function by use of the quantum scattering theory and compare it with the result of a local hidden variable (LHV) theory, 2,15 i.e., Bell's inequality. We also discuss the effect of imperfection of the SPBS in order to make a clear comparison with experiments in the future.In the following we propose a setup which involves the entangler and two S/FS/S junctions, see Fig. 1. The entangler is a device that produces pairs of electrons in a entangled spin singlet.16 . This device can be realized in coupled-semiconductor quantum dots, each of which contains a single electron spin.17-21 The key element of this proposal is the SPBS which ensures the spin up (down) electron leaving the entangler to be transmitted (reflected)...

While Josephson-junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications to new quantum technologies, the low energy quasiparticle excitations characteristically present in these d-wave superconductors may easily destruct the coherence required. Here we demonstrate for the first time the feasibility of macroscopic quantum tunneling in the intrinsic Josephson junctions of a high temperature superconductor Bi2Sr2CaCu2O 8+δ , and find it to be characterized by a high classic-to-quantum crossover temperature and a relatively weak quasiparticle dissipation.PACS numbers: 74.72. Hs, 73.40.Gk, 85.25.Cp A marked feature characterizing cuprate high temperature superconductors (HTSC) is its strong two dimensionality. In particular the bismuth-based HTSCs, for which this anisotropy is prominent, are best viewed as stacks of superconducting CuO 2 planes weakly linked through intrinsic Josephson junction (IJJ) type couplings [1]. These built-in atomic scale links are taylor-made for technical applications difficult to achieve with artificial Josephson junctions (JJ), and its study has now developed into an active interdisciplinary field. We report below what is to our knowledge the first successful observation of the macroscopic quantum tunnelling (MQT) [2,3,4,5] of the phase variable of the superconducting order parameter through the potential barrier of an IJJ, opening up an entirely new direction for HTSC applications. While the corresponding phenomena had been observed at around 300 mK in conventional JJs [3, 5, 6], we have confirmed MQT behavior at approximately 1 K apparently reflecting the characteristically high plasma frequency of IJJs. Our results are highly nontrivial in that they also demonstrate the feasibility of MQT in spite of the presence of dissipative low energy quasiparticles [7,8,9,10], which is the other hallmark of HTSCs.Current-biased JJs offer an ideal stage for realizing a variety of macroscopic quantum phenomena, e.g. energy level quantization within the potential well [4,11,12] and the associated MQT and macroscopic quantum coherence [13,14], all of which have come to be recognized as having immediate implications for qubit applications [13,15,16,17]. In particular, a phase qubit utilizing MQT has been reported by Martinis and co-workers [15].Aside from external noises and disorder, a primary source which stands as an obstacle towards observation of MQT is the influence of non-superconducting quasiparticle excitations [2]. In conventional s-wave superconductors, all quasi-particle states are separated from the superconducting ground state by a finite energy gap and thus become essentially inaccessible upon going to sufficiently low temperatures; hence the observability of MQT. The situation is drastically altered when we turn to HTSCs, which are d-wave superconductors. The latter are characterized by four nodes in the order parameter at which the energy gap vanishes [18,19]. HTSCs therefore necessari...

We examine the macroscopic quantum tunneling (MQT) in high-T c superconductor Josephson junctions with a d-wave order parameter. Using microscopic Hamiltonian and the functional integral method, we analytically obtain the MQT rate (the inverse lifetime of the metastable state) for the c-axis twist Josephson junctions. In the case of the zero twist angle, the system shows the super-Ohmic dissipation due to the presence of the nodal quasiparticle tunneling. Therefore, the MQT rate is strongly suppressed in compared with the finite twist angle cases. PACS numbers: 74.50.+r, 03.65.Yz, 05.30.-d In the current biased Josephson junctions, the states of non-zero supercurrent are metastable owing to transitions to lower-lying minima of the potential. At sufficiently low temperatures, such transitions can be caused by macroscopic quantum tunneling (MQT) 1,2 through the potential barrier. The possibility of observing the MQT in Josephson junctions was first pointed out by Ivanchenko and Zi'lberman. 3 The first clear experimental observations of the MQT were made in 1981 on small s-wave Josephson junctions by Voss and Webb (Nb) 4 and Jackel et al (Pb). 5

We predict anomalous atomic-scale 0-π transitions in a Josephson junction with a ferromagneticinsulator (FI) barrier. The ground state of such junction alternates between 0-and π-states when thickness of FI is increasing by a single atomic layer. We find that the mechanism of the 0-π transition can be attributed to thickness-dependent phase-shifts between the wave numbers of electrons and holes in FI. Based on these results, we show that stable π-state can be realized in junctions based on high-Tc superconductors with La2BaCuO5 barrier.PACS numbers: 74.50.+r, 03.67.Lx The developing field of superconducting spintronics comprises a plenty of fascinating phenomena that may complement nonsuperconducting spintronics devices [1]. Mesoscopic hybrid structures consisting of superconducting and magnetic materials have attracted considerable attention as devices with novel functionalities [2]. One of most interesting effects is the formation of π-states in superconductor/ferromagnetic-metal/superconductor (S/FM/S) Josephson junctions [3]. Under appropriate conditions a ferromagnet can become a π-phase shifter, providing the phase difference φ = π between two superconductors in the ground state in contrast to φ = 0 in ordinary Josephson junctions. Recently a quiet qubit based on S/FM/S π-junction [4] has been suggested as a promising device to realize quantum computation because the spontaneously generated two-level system in this structure is robust against decoherence due to external fluctuations. However, low energy quasiparticle excitations in a FM provide strong dissipation [5]. Therefore Josephson π junctions with a nonmetallic interlayers are highly desired for qubit applications [6]. Moreover, from the fundamental view point, the Josephson transport through a f erromagnetic insulator (FI) has been studied based on phenomenological models [7] and not yet been explored explicitly.In this Letter, we study theoretically the Josephson effect in superconductor/ferromagneticinsulator/superconductor (S/FI/S) junctions using the tight-binding model. We show that the ground state in such structures alternates between the 0-and π-states when the thickness of a FI (L F ) is increasing by a single atomic layer. This remarkable effect originates from the characteristic band structure of a FI. Quasiparticles in the electron and hole branches acquire different phase shifts while propagating across a FI. We will show that the phase difference is exactly πL F due to the band structure of a FI, thus providing the atomic-scale 0-π transition. This mechanism is in striking contrast to the proximity induced 0-π transition in conventional S/FM/S junctions. On the basis of the obtained results, we predict a stable π-state in a Josephson junction based on high-T c superconductors with a La 2 BaCuO 5 barrier, where electric current flows along the c axis of cuprates.Let us first consider an S/FI/S junction in the twodimensional tight-binding model as shown in Fig. 1(a). The vector r = jx + my points to a lattice site, where

Statins have a variety of myotoxic effects and can trigger the development of inflammatory myopathies or myasthenia gravis (MG) mediated by immunomodulatory properties. Autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) have been identified in patients with statin-associated myopathy. The purpose of the present study is to develop an enzyme-linked immunosorbent assay (ELISA) of anti-HMGCR antibodies and to elucidate the clinical significance of anti-HMGCR antibodies in Japanese patients with inflammatory myopathies or MG.We enrolled 75 patients with inflammatory myopathies, who were all negative for anti-signal recognition particle and anti-aminoacyl transfer RNA synthetase antibodies. They were referred to Keio University and National Center of Neurology and Psychiatry between October 2010 and September 2012. We also studied 251 patients with MG who were followed at the MG Clinic at Keio University Hospital. Anti-HMGCR antibodies were detected by ELISA. We investigated demographic, clinical, radiological, and histological findings associated with anti-HMGCR antibodies.We established the anti-HMGCR ELISA with the recombinant protein. Protein immunoprecipitation detected autoantigens corresponding to HMGCR. Immunohistochemistry using muscle biopsy specimens revealed regenerating muscle fibers clearly stained by polyclonal anti-HMGCR antibodies and patients’ serum. Anti-HMGCR autoantibodies were specifically detected in 8 patients with necrotizing myopathy. The seropositivity rate in the necrotizing myopathy patients was significantly higher than those in the patients with other histological diagnoses of inflammatory myopathies (31% vs 2%, P = 0.001). Statins were administered in only 3 of the 8 anti-HMGCR-positive patients. Myopathy associated with anti-HMGCR antibodies showed mild limb weakness and favorable response to immunotherapy. All 8 patients exhibited increased signal intensities on short T1 inversion recovery of muscle MRI. Of the 251 patients with MG, 23 were administered statins at the onset of MG. One late-onset MG patient experienced MG worsening after 4-wk treatment with atorvastatin. However, anti-HMGCR antibodies were not detected in the 251 MG patients except for one early-onset MG patient with no history of statin therapy.Anti-HMGCR antibodies are a relevant clinical marker of necrotizing myopathy with or without statin exposure, but they are not associated with the onset or deterioration of MG.