Coupled spin chains are promising candidates for 'wiring up' qubits in solid-state quantum computing (QC). In particular, two nitrogen-vacancy centers in diamond can be connected by a chain of implanted nitrogen impurities; when driven by a suitable global fields the chain can potentially enable quantum state transfer at room temperature. However, our detailed analysis of error effects suggests that foreseeable systems may fall far short of the fidelities required for QC. Fortunately the chain can function in the more modest role as a mediator of noisy entanglement, enabling QC provided that we use subsequent purification. For instance, a chain of 5 spins with inter-spin distances of 10 nm has finite entangling power as long as the T2 time of the spins exceeds 0.55 ms. Moreover we show that re-purposing the chain this way can remove the restriction to nearest-neighbor interactions, so eliminating the need for complicated dynamical decoupling sequences.Spin chains with nearest neighbor XY coupling mediate coherent interactions between distant spin qubits with fixed locations, and can thus serve as channels to transfer quantum information [1][2][3]. An important application would be to interconnect distant sub-registers of parallel parts in a scalable, solid-state quantum computer [4], e.g. in a diamond-based architecture at room temperature [5]. With an observed roomtemperature coherence time of 1.8 ms [6], the electron spin of individual nitrogen-vacancy (NV − ) defects in diamond is a promising candidate for a qubit [7]: Initialisation, coherent manipulation and measurement with nanoscale resolution (∼ 150 nm) have already been experimentally demonstrated using optical techniques under ambient conditions [8]. In addition, the long-lived 15 N nuclear spin (I = 1/2) associated with each NV − center can act as a local, coherent memory, accessible via the hyperfine coupling [9, 10]. A universal set of quantum operations between the nuclear memory spin and the processing electronic spin qubit within each NV − center is available with microwave and radio-frequency pulses [11][12][13]. Two NV − centers with only a small separation (r 10 nm) may be entangled through direct electron spin dipole-dipole coupling as long as a T 2 time on the order of milliseconds can be maintained [14]. However, individual addressability of the NV − center qubits demands larger separations of several tens or hundreds of nanometers [8], and the direct interaction becomes too weak.A recent proposal [15] suggested a chain of N implanted nitrogen impurities (each with a "dark" electronic spin-1/2) as a coherent quantum channel to transfer quantum states between distant NV − centers at room-temperature (see Fig. 1a). Here, the electron spins of the NV − centers and the nitrogen impurities interact with each other through nearest-neighbor dipoledipole coupling [16, 17]. Importantly, the scheme does not require individual control of the chain spins, instead relying on global resonant driving fields to turn the effective Hamiltonian into an XY exc...
BackgroundThe Traditional Chinese Medicine, arsenic trioxide (ATO, As2O3) could inhibit growth and induce apoptosis in a variety of solid tumor cells, but it is severely limited in the treatment of glioma due to its poor BBB penetration and nonspecifcity distribution in vivo.PurposeThe objective of this study was encapsulating ATO in the modified PAMAM den-drimers to solve the problem that the poor antitumor effect of ATO to glioma, which provide a novel angle for the study of glioma treatment.MethodsThe targeting drug carrier (RGDyC-mPEG-PAMAM) was synthesized based on Arg-Gly-Asp (RGDyC) and αvβ3 integrin targeting ligand, and conjugated to PEGylated fifth generation polyamidoamine dendrimer (mPEG-PAMAM). It was characterized by nuclear magnetic resonance, fourier transform infrared spectra, Nano-particle size-zeta potential analyzer,etc. The in vitro release characteristics were studied by dialysis bag method. MTT assay was used to investigate the cytotoxicity of carriers and the antitumor effect of ATO formulation. In vitro blood-brain barrier (BBB) and C6 cell co-culture models were established to investigate the inhibitory effect of different ATO formulation after transporting across BBB. Pharmacokinetic and antitumor efficacy studies were investigated in an orthotopic murine model of C6 glioma.ResultsThe prepared RGDyC-mPEG-PAMAM was characterized for spherical dendrites, comparable size (21.60±6.81 nm), and zeta potential (5.36±0.22 mV). In vitro release showed that more ATO was released from RGDyC-mPEG-PAMAM/ATO (79.5%) at pH 5.5 than that of pH 7.4, during 48 hours. The cytotoxicity of PEG-modified carriers was lower than that of the naked PAMAM on both human brain microvascular endothelial cells and C6 cells. In in vitro BBB model, modification of RGDyC heightened the cytotoxicity of ATO loaded on PAMAM, due to an increased uptake by C6 cells. The results of cell cycle and apoptosis analysis revealed that RGDyC-mPEG-PAMAM/ATO arrested the cell cycle in G2-M and exhibited threefold increase in percentage of apoptosis to that in the PEG-PAMAM/ATO group. Compared with ATO-sol group, both RGDyC-mPEG-PAMAM/ATO and mPEG-PAMAM/ATO groups prolonged the half-life time, increased area under the curve, and improved antitumor effect, significantly. While the tumor volume inhibitory of RGDyC-mPEG-PAMAM/ATO was 61.46±12.26%, it was approximately fourfold higher than the ATO-sol group, and twofold to the mPEG-PAMAM/ATO group.ConclusionIn this report, RGDyC-mPEG-PAMAM could enhance the antitumor of ATO to glioma, it provides a desirable strategy for targeted therapy of glioma.
Abstract. Recently, a new form of quantum memory was proposed. The storage medium is an ensemble of electron spins, coupled to a stripline cavity and an ancillary readout system. Theoretical studies suggest that the system should be capable of storing numerous qubits within the ensemble, and an experimental proof-of-concept has already been performed. Here, we show that this minimal architecture is not limited to storage but is in fact capable of full quantum processing by employing measurement-based entanglement. The technique appears to be remarkably robust against the anticipated dominant error types. The key enabling component, namely a readout technology that nondestructively determines 'are there n photons in the cavity?', has already been realized experimentally.
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