Randomized Algorithms For High Quality Treatment Planning in Volumetric Modulated Arc Therapy

In recent years, volumetric modulated arc therapy (VMAT) has been becoming a more and more important radiation technique widely used in clinical application for cancer treatment. One of the key problems in VMAT is treatment plan optimization, which is complicated due to the constraints imposed by the involved equipments. In this paper, we consider a model with four major constraints: the bound on the beam intensity, an upper bound on the rate of the change of the beam intensity, the moving speed of leaves of the multi-leaf collimator (MLC) and its directional-convexity. We solve the model by a two-stage algorithm: performing minimization with respect to the shapes of the aperture and the beam intensities alternatively. Specifically, the shapes of the aperture are obtained by a greedy algorithm whose performance is enhanced by random sampling in the leaf pairs with a decremental rate. The beam intensity is optimized using a gradient projection method with non-monotonic line search. We further improve the proposed algorithm by an incremental random importance sampling of the voxels to reduce the computational cost of the energy functional. Numerical simulations on two clinical cancer date sets demonstrate that our method is highly competitive to the state-of-the-art algorithms in terms of both computational time and quality of treatment planning

Measurement-device-independent quantum key distribution with source state errors in photon number space

The existing decoy-state MDI-QKD theory assumes the perfect control of the source states which is a an impossible task for any real setup. In this paper, we study the decoy-state MDI-QKD method with source errors without any presumed conditions and we get the final security key rate only with the range of a few parameters in the source state.Comment: Published in PRA in Dec. 2016. We present formula for the MDIQKD with an unstable source, i.e., in the case there are intensity errors. Our general formula applies to almost all types of sources, such as WCS, HSPS, the passive decoy state protocol and so on. arXiv admin note: text overlap with arXiv:1710.0821

Critical phenomena and chemical potential of charged AdS black hole

We study the thermodynamics and the chemical potential for a five-dimensional charged AdS black hole by treating the cosmological constant as the number of colors $N$ in the boundary gauge theory and its conjugate quantity as the associated chemical potential $\mu$. It is found that there exists a small-large black hole phase transition. The critical phenomena are investigated in the $N^{2}$-$\mu$ chart. In particular, in the reduced parameter space, all the thermodynamic quantities can be rescaled with the black hole charge such that these reduced quantities are charge-independent. Then we obtain the coexistence curve and the phase diagram. The latent heat is also numerically calculated. Moreover, the heat capacity and the thermodynamic scalar are studied. The result indicates that the information of the first-order black hole phase transition is encoded in the heat capacity and scalar. However, the phase transition point cannot be directly calculated with them. Nevertheless, the critical point linked to a second-order phase transition can be determined by either the heat capacity or the scalar. In addition, we calculate the critical exponents of the heat capacity and the scalar for the saturated small and large black holes near the critical point.Comment: 17 pages, 17 figure

Quasinormal Modes and Van der Waals like phase transition of charged AdS black holes in Lorentz symmetry breaking massive gravity

Using the quasinormal modes of a massless scalar perturbation, we investigate the small/large black hole phase transition in the Lorentz symmetry breaking massive gravity. We mainly focus on two issues: i) the sign change of slope of the quasinormal mode frequencies in the complex-$\omega$ diagram; ii) the behaviors of the imaginary part of the quasinormal mode frequencies along the isobaric or isothermal processes. For the first issue, our result shows that, at low fixed temperature or pressure, the phase transition can be probed by the sign change of slope. While increasing the temperature or pressure to some certain values near the critical point, there will appear the deflection point, which indicates that such method may not be appropriate to test the phase transition. In particular, the behavior of the quasinormal mode frequencies for the small and large black holes tend to the same at the critical point. For the second issue, it is shown that the non-monotonic behavior is observed only when the small/large black hole phase transition occurs. Therefore, this property can provide us with an additional method to probe the phase transition through the quasinormal modes.Comment: 12 pages, 10 figures, and 2 table

Measurement-device-independent quantum key distribution with source state errors and statistical fluctuation

We show how to calculate the secure final key rate in the four-intensity decoy-state MDI-QKD protocol with both source errors and statistical fluctuations with a certain failure probability. Our results rely only on the range of only a few parameters in the source state. All imperfections in this protocol have been taken into consideration without any unverifiable error patterns.Comment: Published in PRA in March 2017. We present general results for MDIQKD with both intensity error of source and statistical fluctuatio

Sending or not sending: twin-field quantum key distribution with large misalignment error

Based on the novel idea of twin-field quantum key distribution, we present a sending-or-not-sending twin-field fault tolerant quantum key distribution protocol. Our protocol can access a secure distance longer than 700 km even though the misalignment error rate is $15\%$. In the case of zero alignment error, our protocol can exceeds a secure distance of 800 km. Thanks to the novel idea of TF-QKD !Comment: 13 pages, 3 figure

Quantum-Limited Amplification of Cavity Optomechanics without Resolved Sideband Condition

We propose a scheme to realize the phase-preserving amplification without the restriction of resolved sideband condition. As a result, our gain-bandwidth product is about one magnitude larger than the existing proposals. In our model, an additional cavity is coupled to the cavity-optomechanical system. Therefore our operating frequency is continuously tunable via adjusting the coupling coefficient of the two cavities.Comment: 6 pages,11 figure

Decoy state method for measurement device independent quantum key distribution with different intensities in only one basis

We show that the three-intensity protocol for measurement device independent quantum key distribution (MDI QKD) can be done with different light intensities in {\em only one} basis. Given the fact that the exact values yields of single-photon pairs in the $X$ and $Z$ bases must be the same, if we have lower bound of the value in one basis, we can also use this as the lower bound in another basis. Since in the existing set-up for MDI-QKD, the yield of sources in different bases are normally different, therefore our method can improve the key rate drastically if we choose to only use the lower bound of yield of single-photon pairs in the advantageous basis. Moreover, since our proposal here uses fewer intensities of light, the probability of intensity mismatch will be smaller than the existing protocols do. This will further improve the advantage of our method. The advantage of using Z basis or X basis of our method is studied and significant improvement of key rates are numerically demonstrated.Comment: arXiv admin note: substantial text overlap with arXiv:1308.567

Encoding-side-channel-free and measurement-device-independent quantum key distribution

We present a simple protocol where Alice and Bob only needs sending out a coherent state or not-sending out a coherent state to Charlie. There is no bases switching. We show that this protocol is both encoding-state-side-channel free to the source part and measurement-device-independent. We don't have to control exactly the whole space state of the light pulse, which is an impossible task in practice. The protocol is immune to all adverse due to encoding-state imperfections in side-channel space such as the photon frequency spectrum, emission time, propagation direction, spatial angular moment, and so on. Numerical simulation shows that our scheme can reach a side-channel-free result for quantum key distribution over a distance longer than 200 km given the single-photon-interference misalignment error rate of $20\%$.Comment: 12 pages, 2 figure

Effective Eavesdropping to Twin Field Quantum Key Distribution

We present an effective Eavesdropping scheme to attack the twin-field protocol of quantum key distribution [TF-QKD] proposed recently