11,475 research outputs found
Detecting fractional Josephson effect through phase slip
Fractional Josephson effect is a unique character of Majorana Fermions in
topological superconductor system. This effect is very difficult to detect
experimentally because of the disturbance of quasiparticle poisoning and
unwanted couplings in the superconductor. Here, we propose a scheme to probe
fractional DC Josephson effect of semiconductor nanowire-based topological
Josephson junction through 4{\pi} phase slip. By exploiting a topological RF
SQUID system we find that the dominant contribution for Josephson coupling
comes from the interaction of Majorana Fermions, resulting the resonant
tunneling with 4{\pi} phase slip. Our calculations with experimentally
reachable parameters show that the time scale for detecting the phase slip is
two orders of magnitude shorter than the poisoning time of nonequilibrium
quasiparticles. Additionally, with a reasonable nanowire length the 4{\pi}
phase slip could overwhelm the topological trivial 2{\pi} phase slip. Our work
is meaningful for exploring the effect of modest quantum fluctuations of the
phase of the superconductor on the topological system, and provide a new method
for quantum information processing.Comment: 5 pages, 3 figure
Detecting fractional Josephson effect through phase slip
Fractional Josephson effect is a unique character of Majorana Fermions in
topological superconductor system. This effect is very difficult to detect
experimentally because of the disturbance of quasiparticle poisoning and
unwanted couplings in the superconductor. Here, we propose a scheme to probe
fractional DC Josephson effect of semiconductor nanowire-based topological
Josephson junction through 4{\pi} phase slip. By exploiting a topological RF
SQUID system we find that the dominant contribution for Josephson coupling
comes from the interaction of Majorana Fermions, resulting the resonant
tunneling with 4{\pi} phase slip. Our calculations with experimentally
reachable parameters show that the time scale for detecting the phase slip is
two orders of magnitude shorter than the poisoning time of nonequilibrium
quasiparticles. Additionally, with a reasonable nanowire length the 4{\pi}
phase slip could overwhelm the topological trivial 2{\pi} phase slip. Our work
is meaningful for exploring the effect of modest quantum fluctuations of the
phase of the superconductor on the topological system, and provide a new method
for quantum information processing.Comment: 5 pages, 3 figure
On Reinforcement Learning for Full-length Game of StarCraft
StarCraft II poses a grand challenge for reinforcement learning. The main
difficulties of it include huge state and action space and a long-time horizon.
In this paper, we investigate a hierarchical reinforcement learning approach
for StarCraft II. The hierarchy involves two levels of abstraction. One is the
macro-action automatically extracted from expert's trajectories, which reduces
the action space in an order of magnitude yet remains effective. The other is a
two-layer hierarchical architecture which is modular and easy to scale,
enabling a curriculum transferring from simpler tasks to more complex tasks.
The reinforcement training algorithm for this architecture is also
investigated. On a 64x64 map and using restrictive units, we achieve a winning
rate of more than 99\% against the difficulty level-1 built-in AI. Through the
curriculum transfer learning algorithm and a mixture of combat model, we can
achieve over 93\% winning rate of Protoss against the most difficult
non-cheating built-in AI (level-7) of Terran, training within two days using a
single machine with only 48 CPU cores and 8 K40 GPUs. It also shows strong
generalization performance, when tested against never seen opponents including
cheating levels built-in AI and all levels of Zerg and Protoss built-in AI. We
hope this study could shed some light on the future research of large-scale
reinforcement learning.Comment: Appeared in AAAI 201
Theoretical analysis of direct violation and differential decay width in in phase space around the resonances and
We perform a theoretical study on direct violation in in phase space around the intermediate states and
. The possible interference between the amplitudes corresponding to
the two resonances is taken into account, and the relative strong phase of the
two amplitudes is treated as a free parameter. Our analysis shows that by
properly chosen the strong phase, both the violation strength and
differential decay width accommodate to the experimental results.Comment: 15 pages, 5 figure
An apparent positive relation between spin and orbital angular momentum in X-ray binaries
The origin of current angular momentum (AM) of the black hole (BH) in X-ray
binary (XRB) is still unclear, which is related with the birth and/or the
growth of the BH. Here we collect the spin parameters measured in BH
XRBs and find an apparent bimodal distribution centered at 0.17 and
0.83. We find a positive relation between the spin parameter and the orbital
period/orbital separation through combining distinct XRB categories, including
neutron star (NS) low-mass X-ray binaries (LMXBs), Roche-lobe overflow (RLOF)
BH XRBs and wind-fed BH XRBs. It seems that the AM of the compact star and the
binary orbit correlates by combining the different XRB systems. These positive
relations imply that accretion process is a common mechanism for spinning up
the compact star in these diverse XRB systems. We infer that the low and high
spin BH XRBs may experience different evolution and accretion history, which
corresponds to the bimodal distribution of the BH spin parameters. The low spin
BHs () are similar to the NS LMXBs, the compact star of which is
spun-up by the low-level accretion, and the high spin BHs () had
experienced a short hypercritical accretion ()
period, during which, the BH spin dramatically increased.Comment: 13 pages, 7 figures, accepted for publication in MNRA
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