Limited population-based cancer registry data available in China until now has hampered efforts to inform cancer control policy. Following extensive efforts to improve the systematic cancer surveillance in this country, we report on the largest pooled analysis of cancer survival data in China to date. Of 21 population-based cancer registries, data from 17 registries (n 5 138,852 cancer records) were included in the final analysis. Cases were diagnosed in 2003-2005 and followed until the end of 2010. Age-standardized relative survival was calculated using region-specific life tables for all cancers combined and
After analysing the main quantum secret sharing protocol based on the entanglement states, we propose an idea to directly encode the qubit of quantum key distributions, and then present a quantum secret sharing scheme where only product states are employed. As entanglement, especially the inaccessable multi-entangled state, is not necessary in the present quantum secret sharing protocol, it may be more applicable when the number of the parties of secret sharing is large. Its theoretic efficiency is also doubled to approach 100%.Comment: 2 tables, to appear in Phys. Lett.
We investigate the low-temperature magneto-transport properties of individual Ge/Si core/shell nanowires. Negative magneto-conductance was observed, which is a signature of one-dimensional weak antilocalization of holes in the presence of strong spin--orbit coupling. The temperature and back gate dependences of phase coherence length, spin--orbit relaxation time, and background conductance were studied. Specifically, we show that the spin--orbit coupling strength can be modulated by more than five folds with an external electric field. These results suggest the Ge/Si nanowire system possesses strong and tunable spin--orbit interactions and may serve as a candidate for spintronics applications.
A basic requirement for quantum information processing is the ability to universally control the state of a single qubit on timescales much shorter than the coherence time. Although ultrafast optical control of a single spin has been achieved in quantum dots, scaling up such methods remains a challenge. Here we demonstrate complete control of the quantum-dot charge qubit on the picosecond scale, orders of magnitude faster than the previously measured electrically controlled charge- or spin-based qubits. We observe tunable qubit dynamics in a charge-stability diagram, in a time domain, and in a pulse amplitude space of the driven pulse. The observations are well described by Landau–Zener–Stückelberg interference. These results establish the feasibility of a full set of all-electrical single-qubit operations. Although our experiment is carried out in a solid-state architecture, the technique is independent of the physical encoding of the quantum information and has the potential for wider applications.
Here we present a quantum electrodynamics (QED) model involving a large-detuned single-mode cavity field and n identical two-level atoms. One of its applications for the preparation of the multiparticle states is analyzed. In addition to the Greenberger-Horne-Zeilinger (GHZ) state, the W class states can also be generated in this scheme. The further analysis for the experiment of the model of n = 2 case is also presented by considering the possible three-atom collision.PACS ) was shown by Bell [3] to have stronger correlations than allowed by any local hidden variable theory. For the multi-particle entanglement states, there are many properties more peculiar than the two-party ones. For example, the Greenberger-HorneZeilinger (GHZ) state [4,5] Φ ABC = 1 √ 2 (|111 ± |000 ), a canonical three-particle entanglement state exhibits the contradiction between local hidden variable theories and quantum mechanics even for nonstatistical predictions, as opposed to the statistical ones for the EPR states. Many papers have discussed the multiparticle entanglement and its applications [6,7]. In the paper [8], the authors proved that there exists another kind of peculiar genuine tripartite entanglement W states W = 1 √ 3 (|001 + |010 + |100 ), which is inequivalent to the GHZ states in the sense that they cannot been converted to each other even under stochastic local operations and classical communication (SLOCC); that is, through LOCC but without imposing that it has to be achieved with certainty [9]. The GHZ state is maximally in several senses [10], for instance, it maximally violates Bell-type inequalities, the mutual information of measurement outcomes is maximal, it is maximally stable against (white) noise and one can locally obtain from a GHZ state with unit probability an EPR state shared between any two of the three parties. Another relevant feature is that when any one of the three qubits is traced out, the remaining two are in separable -and therefore unentangled -state. Thus, the entanglement properties of the GHZ state are very fragile under particle losses. Oppositely, the entanglement of the W state has the highest degree of endurance against loss of one of the three qubits which is argued as an important property in any situation where one of the three parties decide not to cooperate with the other two [8]. For the generalized form W n = 1 √ n |n − 1, 1 , where |n − 1, 1 denotes the totally symmetric state including n − 1 zeros and 1 ones, the concurrence (which is related to the formation entanglement) of any reduced density operators ρ k.u , C k,u (ρ k.u ) = 2/n, which indicates the maximal entanglement achievable for any reduced two parties of system in any pure state [8,11]. The states which can been converted to each other under SLOCC belong to the same class, then there are at least two inequivalent classes of multiparticle entanglement states: the GHZ state class and the W state class [8].Recently, it has been realized that quantum resources can be useful in information processing where quantum entang...
Solid-state color centers with manipulable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which the telecomwavelength emission is detected. Through carefully optimizing the implanted conditions, we improve the concentration of NV centers for about 4 times. Based on this, the coherent control of NV center spins is achieved at room temperature and the coherence time T2 * can be reached around 1 μs. Furthermore, the investigation of fluorescence properties of single NV centers shows that they are room temperature photostable single photon sources at telecom range. Taking the advantages of the technological mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising systems for large-scale integrated quantum photonics and long-distance quantum networks.
Classical simulations of quantum circuits are limited in both space and time when the qubit count is above 50, the realm where quantum supremacy reigns. However, recently, for the low depth circuit with more than 50 qubits, there are several methods of simulation proposed by teams at Google and IBM. Here, we present a scheme of simulation which can extract a large amount of measurement outcomes within a short time, achieving a 64-qubit simulation of a universal random circuit of depth 22 using a 128-node cluster, and 56-and 42-qubit circuits on a single PC. We also estimate that a 72-qubit circuit of depth 23 can be simulated in about 16 h on a supercomputer identical to that used by the IBM team. Moreover, the simulation processes are exceedingly separable, hence parallelizable, involving just a few inter-process communications. Our work enables simulating more qubits with less hardware burden and provides a new perspective for classical simulations.
ABSTRACT:We have developed an etching process to fabricate a quantum dot and a nearby single electron transistor as a charge detector in a single layer graphene. The high charge sensitivity of the detector is used to probe Coulomb diamonds as well as excited spectrum in the dot, even in the regime where the current through the quantum dot is too small to be measured by conventional transport means.The graphene based quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit in a nuclear-spin-free quantum world.
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