Quantum squeezing-induced quantum entanglement and EPR steering in a coupled optomechanical system.

We propose a theoretical project in which quantum squeezing induces quantum entanglement and Einstein-Podolsky-Rosen steering in a coupled whispering-gallery-mode optomechanical system. Through pumping the χ(2)-nonlinear resonator with the phase matching condition, the generated squeezed resonator mode and the mechanical mode of the optomechanical resonator can generate strong quantum entanglement and EPR steering, where the squeezing of the nonlinear resonator plays the vital role. The transitions from zero entanglement to strong entanglement and one-way steering to two-way steering can be realized by adjusting the system parameters appropriately. The photon-photon entanglement and steering between the two resonators can also be obtained by deducing the amplitude of the driving laser. Our project does not need an extraordinarily squeezed field, and it is convenient to manipulate and provides a novel and flexible avenue for diverse applications in quantum technology dependent on both optomechanical and photon-photon entanglement and steering.

Release of virtual photon and phonon pairs from qubit-plasmon-phonon ultrastrong coupling system.

The most important difference between ultrastrong and non-ultrastrong coupling regimes is that the ground state contains excitations. We consider a qubit-plasmon-phonon ultrastrong coupling (USC) system with a three-level atom coupled to the photon and phonon via its upper two energy levels and show that spontaneous emission of the atom from its intermediate to its ground state produces photon and phonon pairs. It is shown that the current system can produce a strong photon/phonon stream and the atom-phonon coupling plays the active role, which ensures the experimental detection. The emission spectrum and various high-order correlation functions confirm the generation of the pairs of photons and phonons. Our study has important implications for future research on virtual photon and phonon pairs creation in the ground state of the USC regime.

Photon blockade with a trapped Λ-type three-level atom in asymmetrical cavity.

We propose a scheme to manipulate strong and nonreciprocal photon blockades in asymmetrical Fabry-Perot cavity with a Λ-type three-level atom. Utilizing the mechanisms of both conventional and unconventional blockade, the strong photon blockade is achieved by the anharmonic eigenenergy spectrum brought by Λ-type atom and the destructive quantum interference effect induced by a microwave field. By optimizing the system parameters, the manipulation of strong photon blockade over a wide range of cavity detuning can be realized. Using spatial symmetry breaking introduced by the asymmetry of cavity, the direction-dependent nonreciprocal photon blockade can be achieved, and the nonreciprocity can reach the maximum at optimal cavity detuning. In particular, manipulating the occurring position of nonreciprocal photon blockade can be implemented by simply adjusting the cavity detuning. Our scheme provides feasible access for generating high-quality nonreciprocal single-photon sources.

Mechanically controllable nonreciprocal transmission and perfect absorption of photons.

Photon absorption and nonreciprocal photon transmission are studied in a rotating optical resonator coupled with an atomic ensemble. It is demonstrated that the perfect photon absorption is accompanied by optical bistability when the resonator is static. If the spinning detune is adjusted to some particular values, we find that the amplified unidirectional photon transmission can be realized. We have explicitly given the perfect photon absorption conditions and the maximal adjustable amplification rate. It is found that the coupling of the resonator and the atomic ensemble is necessary for perfect photon absorption, and the phase difference of the two input fields only affects the perfect absorption point. It gives new insight into the design of photon absorbers and optical switches.

Common Environmental Effects on Quantum Thermal Transistor.

Quantum thermal transistor is a microscopic thermodynamical device that can modulate and amplify heat current through two terminals by the weak heat current at the third terminal. Here we study the common environmental effects on a quantum thermal transistor made up of three strong-coupling qubits. It is shown that the functions of the thermal transistor can be maintained and the amplification rate can be modestly enhanced by the skillfully designed common environments. In particular, the presence of a dark state in the case of the completely correlated transitions can provide an additional external channel to control the heat currents without any disturbance of the amplification rate. These results show that common environmental effects can offer new insights into improving the performance of quantum thermal devices.

Creation of superposition of arbitrary states encoded in two high-Q cavities.

The principle of superposition is a key ingredient for quantum mechanics. A recent work [Phys. Rev. Lett.116, 110403 (2016)10.1103/PhysRevLett.116.110403] has shown that a quantum adder that deterministically generates a superposition of two unknown states is forbidden. Here we consider the implementation of the probabilistic quantum adder in the 3D cavity-transmon system. Our implementation is based on a three-level superconducting transmon qubit dispersively coupled to two cavities. Numerical simulations show that high-fidelity generation of the superposition of two coherent states is feasible with current circuit QED technology. Our method also works for other physical systems such as two optical cavities coupled to a three-level atom or two nitrogen-vacancy center ensembles interacted with one three-level superconducting flux qubit.

One-step implementation of a hybrid Fredkin gate with quantum memories and single superconducting qubit in circuit QED and its applications.

In a recent remarkable experiment [Sci. Adv. 2, e1501531 (2016)], a 3-qubit quantum Fredkin (i.e., controlled-SWAP) gate was demonstrated by using linear optics. Here we propose a simple experimental scheme by utilizing the dispersive interaction in superconducting quantum circuit to implement a hybrid Fredkin gate with a superconducting flux qubit as the control qubit and two separated quantum memories as the target qudits. The quantum memories considered here are prepared by the superconducting coplanar waveguide resonators or nitrogen-vacancy center ensembles. In particular, it is shown that this Fredkin gate can be realized using a single-step operation and more importantly, each target qudit can be in an arbitrary state with arbitrary degrees of freedom. Furthermore, we show that this experimental scheme has many potential applications in quantum computation and quantum information processing such as generating arbitrary entangled states (discrete-variable states or continuous-variable states) of the two memories, measuring the fidelity and the entanglement between the two memories. With state-of-the-art circuit QED technology, the numerical simulation is performed to demonstrate that two-memory NOON states, entangled coherent states, and entangled cat states can be efficiently synthesized.

Whole-genome sequencing of cultivated and wild peppers provides insights into Capsicum domestication and specialization.

As an economic crop, pepper satisfies people's spicy taste and has medicinal uses worldwide. To gain a better understanding of Capsicum evolution, domestication, and specialization, we present here the genome sequence of the cultivated pepper Zunla-1 (C. annuum L.) and its wild progenitor Chiltepin (C. annuum var. glabriusculum). We estimate that the pepper genome expanded ∼0.3 Mya (with respect to the genome of other Solanaceae) by a rapid amplification of retrotransposons elements, resulting in a genome comprised of ∼81% repetitive sequences. Approximately 79% of 3.48-Gb scaffolds containing 34,476 protein-coding genes were anchored to chromosomes by a high-density genetic map. Comparison of cultivated and wild pepper genomes with 20 resequencing accessions revealed molecular footprints of artificial selection, providing us with a list of candidate domestication genes. We also found that dosage compensation effect of tandem duplication genes probably contributed to the pungent diversification in pepper. The Capsicum reference genome provides crucial information for the study of not only the evolution of the pepper genome but also, the Solanaceae family, and it will facilitate the establishment of more effective pepper breeding programs.

Relationship Between P15 Gene Mutation and Formation and Metastasis of Malignant Osteosarcoma.

BACKGROUND As a type of primary malignant bone tumor, osteosarcoma has high incidence and poor prognosis, and is predisposed for pulmonary metastasis. The abnormal expression of P15 gene directly participates in the invasion of various cancers. Therefore, this study investigated the gene mutation of P15 in both primary lesion and pulmonary metastasis lesion of osteosarcoma in a rat model, in an attempt to elucidate the value of P15 gene as a biological marker. MATERIAL AND METHODS A total of 60 SD rats were randomly divided into 2 groups. Model rats had injection of osteosarcoma UMR-106 cells (5×106) inoculated underneath the right forelimb skin, while control rats received saline injection instead. Six rats were sacrificed after 0, 1, 2, 4, and 6 weeks of the inoculation. Tissue samples from inoculation sites and lungs were extracted for measuring the tumor size. SP immunohistochemical (IHC) staining was used to detect the positive expression rate, while P15 gene mutation was detected by PCR method. RESULTS With the elongation of inoculation time, tumor size was significantly increased (p<0.05). The positive expression rates in both primary and pulmonary metastasis lesions were also significantly elevated (p<0.05). The occurrence rate of P15 gene mutation in model rats was significantly elevated and showed a correlation with the tumor formation (r=0.998, p<0.05). CONCLUSIONS The P15 gene mutation was significantly correlated with osteosarcoma formation and metastasis towards the pulmonary tissue, suggesting its potency as a novel biological marker for early diagnosis of osteosarcoma.

Magnetically controlled quantum thermal devices via three nearest-neighbor coupled spin-1/2 systems.

A quantum thermal device based on three nearest-neighbor coupled spin-1/2 systems controlled by the magnetic field is proposed. We systematically study the steady-state thermal behaviors of the system. When the two terminals of our system are in contact with two thermal reservoirs, respectively, the system behaves as a perfect thermal modulator that can manipulate heat current from zero to specific values by adjusting magnetic-field direction over different parameter ranges, since the longitudinal magnetic field can completely block the heat transport. Significantly, the modulator can also be achieved when a third thermal reservoir perturbs the middle spin. We also find that the transverse field can induce the system to separate into two subspaces in which neither steady-state heat current vanishes, thus providing an extra level of control over the heat current through the manipulation of the initial state. In addition, the performance of this device as a transistor can be enhanced by controlling the magnetic field, achieving versatile amplification behaviors, in particular substantial amplification factors.

Quantum heat valve and diode of strongly coupled defects in amorphous material.

The mechanical strain can control the frequency of two-level atoms in amorphous material. In this work, we would like to employ two coupled two-level atoms to manipulate the magnitude and direction of heat transport by controlling mechanical strain to realize the function of a thermal switch and valve. It is found that a high-performance heat diode can be realized in the wide piezo voltage range at different temperatures. We also discuss the dependence of the rectification factor on temperatures and couplings of heat reservoirs. We find that the higher temperature differences correspond to the larger rectification effect. The asymmetry system-reservoir coupling strength can enhance the magnitude of heat transfer, and the impact of asymmetric and symmetric coupling strength on the performance of the heat diode is complementary. It may provide an efficient way to modulate and control heat transport's magnitude and flow preference. This work may give insight into designing and tuning quantum heat machines.

Dual-Targeted Novel Temozolomide Nanocapsules Encapsulating siPKM2 Inhibit Aerobic Glycolysis to Sensitize Glioblastoma to Chemotherapy.

Chemotherapy of glioblastoma (GBM) has not yielded success due to inefficient blood-brain barrier (BBB) penetration and poor glioma tissue accumulation. Aerobic glycolysis, as the main mode of energy supply for GBM, safeguards the rapid growth of GBM while affecting the efficacy of radiotherapy and chemotherapy. Therefore, to effectively inhibit aerobic glycolysis, increase drug delivery efficiency and sensitivity, a novel temozolomide (TMZ) nanocapsule (ApoE-MT/siPKM2 NC) is successfully designed and prepared for the combined delivery of pyruvate kinase M2 siRNA (siPKM2) and TMZ. This drug delivery platform uses siPKM2 as the inner core and methacrylate-TMZ (MT) as the shell component to achieve inhibition of glioma energy metabolism while enhancing the killing effect of TMZ. By modifying apolipoprotein E (ApoE), dual targeting of the BBB and GBM is achieved in a "two birds with one stone" style. The glutathione (GSH) responsive crosslinker containing disulfide bonds ensures "directional blasting" cleavage of the nanocapsules to release MT and siPKM2 in the high GSH environment of glioma cells. In addition, in vivo experiments verify that ApoE-MT/siPKM2 NC has good targeting ability and prolongs the survival of tumor-bearing nude mice. In summary, this drug delivery system provides a new strategy for metabolic therapy sensitization chemotherapy.

Quantum thermal diode dominated by pure classical correlation via three triangular-coupled qubits.

A quantum thermal diode is designed based on three pairwise coupled qubits, two connected to a common reservoir and the other to an independent reservoir. It is found that the internal couplings between qubits can enhance heat currents. If the two identical qubits uniformly couple with the common reservoir, the crossing dissipation will occur, leading to the initial-state-dependent steady state, which can be decomposed into the mixture of two particular steady states: the heat-conducting state generating maximum heat current and the heat-resisting state not transporting heat. However, the rectification factor doesn't depend on the initial state. In particular, we find that neither quantum entanglement nor quantum discord is present in the steady state, but the pure classical correlation shows a remarkably consistent behavior as the heat rectification factor, which reveals the vital role of classical correlation in the system.

Quantum heat diode versus light emission in circuit quantum electrodynamical system.

Precisely controlling heat transfer in a quantum mechanical system is particularly significant for designing quantum thermodynamical devices. With the technology of experiment advances, circuit quantum electrodynamics (circuit QED) has become a promising system due to controllable light-matter interactions as well as flexible coupling strengths. In this paper, we design a thermal diode in terms of the two-photon Rabi model of the circuit QED system. We find that the thermal diode can not only be realized in the resonant coupling but also achieve better performance, especially for the detuned qubit-photon ultrastrong coupling. We also study the photonic detection rates and their nonreciprocity, which indicate similar behaviors with the nonreciprocal heat transport. This provides the potential to understand thermal diode behavior from the quantum optical perspective and could shed new insight into the relevant research on thermodynamical devices.

Quantum speed limit based on the bound of Bures angle.

In this paper, we investigate the unified bound of quantum speed limit time in open systems based on the modified Bures angle. This bound is applied to the damped Jaynes-Cummings model and the dephasing model, and the analytical quantum speed limit time is obtained for both models. As an example, the maximum coherent qubit state with white noise is chosen as the initial states for the damped Jaynes-Cummings model. It is found that the quantum speed limit time in both the non-Markovian and the Markovian regimes can be decreased by the white noise compared with the pure state. In addition, for the dephasing model, we find that the quantum speed limit time is not only related to the coherence of initial state and non-Markovianity, but also dependent on the population of initial excited state.

Multifunctional quantum thermal device utilizing three qubits.

Quantum thermal devices which can manage heat as their electronic analogs for the electronic currents have attracted increasing attention. Here a three-terminal quantum thermal device is designed by three coupling qubits interacting with three heat baths with different temperatures. Based on the steady-state behavior solved from the dynamics of this system, it is demonstrated that such a device integrates multiple interesting thermodynamic functions. It can serve as a heat current transistor to use the weak heat current at one terminal to effectively amplify the currents through the other two terminals, to continuously modulate them ranging in a large amplitude, and even to switch on or off the heat currents. It is also found that the three currents are not sensitive to the fluctuation of the temperature at the low-temperature terminal, so it can behave as a thermal stabilizer. In addition, we can utilize one terminal temperature to ideally turn off the heat current at any one terminal and to allow the heat currents through the other two terminals, so it can be used as a thermal valve. Finally, we illustrate that this thermal device can control the heat currents to flow unidirectionally, so it has the function of a thermal rectifier.

Coherence measure in terms of the Tsallis relative α entropy.

Coherence is the most fundamental quantum feature of the nonclassical systems. The understanding of coherence within the resource theory has been attracting increasing interest among which the quantification of coherence is an essential ingredient. A satisfactory measure should meet certain standard criteria. It seems that the most crucial criterion should be the strong monotonicity, that is, average coherence doesn't increase under the (sub-selective) incoherent operations. Recently, the Tsallis relative α entropy has been tried to quantify the coherence. But it was shown to violate the strong monotonicity, even though it can unambiguously distinguish the coherent and the incoherent states with the monotonicity. Here we establish a family of coherence quantifiers which are closely related to the Tsallis relative α entropy. It proves that this family of quantifiers satisfy all the standard criteria and particularly cover several typical coherence measures.

Quantum thermal transistor based on qubit-qutrit coupling.

A quantum thermal transistor is designed by the strong coupling between one qubit and one qutrit which are in contact with three heat baths with different temperatures. The thermal behavior is analyzed based on the master equation by both the numerical and the approximately analytic methods. It is shown that the thermal transistor, as a three-terminal device, allows a weak modulation heat current (at the modulation terminal) to switch on and off and effectively modulate the heat current between the other two terminals. In particular, the weak modulation heat current can induce the strong heat current between the other two terminals with the multiple-region amplification of heat current. Furthermore, the heat currents are quite robust to the temperature (current) fluctuation at the lower-temperature terminal within a certain range of temperature, and so it can behave as a heat current stabilizer.

Enabling the self-contained refrigerator to work beyond its limits by filtering the reservoirs.

In this paper, we study the quantum self-contained refrigerator [Linden et al., Phys. Rev. Lett. 105, 130401 (2010)PRLTAO0031-900710.1103/PhysRevLett.105.130401] in the strong internal coupling regime with engineered reservoirs. We find that if some modes of the three thermal reservoirs can be properly filtered out, the efficiency and the working domain of the refrigerator can be improved in contrast to the those in the weak internal coupling regime, which indicates one advantage of the strong internal coupling. In addition, we find that the background natural vacuum reservoir could cause the filtered refrigerator to stop working and the background natural thermal reservoir could greatly reduce the cooling efficiency.

The classical correlation limits the ability of the measurement-induced average coherence.

Coherence is the most fundamental quantum feature in quantum mechanics. For a bipartite quantum state, if a measurement is performed on one party, the other party, based on the measurement outcomes, will collapse to a corresponding state with some probability and hence gain the average coherence. It is shown that the average coherence is not less than the coherence of its reduced density matrix. In particular, it is very surprising that the extra average coherence (and the maximal extra average coherence with all the possible measurements taken into account) is upper bounded by the classical correlation of the bipartite state instead of the quantum correlation. We also find the sufficient and necessary condition for the null maximal extra average coherence. Some examples demonstrate the relation and, moreover, show that quantum correlation is neither sufficient nor necessary for the nonzero extra average coherence within a given measurement. In addition, the similar conclusions are drawn for both the basis-dependent and the basis-free coherence measure.