Tunable high-order sideband generation in a coupled double-cavity optomechanical system.

Tunable high-order sideband generation has important applications in the realization of the optical frequency comb with a varying spectral region (corresponding to the sideband range) and frequency resolution (corresponding to the sideband interval). In this paper, we propose a theoretical scheme to tune both the range and the interval of the high-order sidebands in a coupled double-cavity optomechanical system, which consists of an optomechanical cavity and an auxiliary cavity. Our proposal can be realized by driving the optomechanical cavity with a control field and a probe field simultaneously, driving the auxiliary cavity with a pump field. Furthermore, we assume that the frequency detuning between the control field and the probe field (the pump field) equals ωb/n (ωb/m), where ωb is the mechanical frequency, m and n are integers. When n = m = 1, we find that the sideband range can be effectively enlarged by increasing the pump amplitude or the photon-hopping coupling rate, or by decreasing the auxiliary cavity damping rate. When n = 1 and m > 1, the output spectrum consists of a series of integer-order sidebands, fraction-order sidebands, and the sum and difference sidebands, and the sideband interval becomes ωb/m and can be diminished by simultaneously increasing m and the pump amplitude.

Proof-of-principle demonstration of measurement-device-independent quantum key distribution based on intrinsically stable polarization-modulated units.

The experimental demonstration of measurement-device-independent quantum key distribution (MDI-QKD) has been widely demonstrated. Thus far, several experimental groups have implemented polarization encoding MDI-QKD but with manual polarization controllers, or polarization modulators that make circular polarization states unstable. Here, we apply an intrinsically stable polarization-modulated unit (PMU) to MDI-QKD so that Alice and Bob can modulate four BB84 polarization states, all of which can be kept stable from even the harsh environment. Moreover, our PMU can provide two operational polarization encoding modes suitable to different application scenarios. A proof-of-principle demonstration of MDI-QKD based on our PMU is implemented with an interference visibility of 46.6%, an average quantum bit error rate of 1.49% for the Z basis and the secure key rate of 4.25 × 10-6 bits per pulse. The proposed study is helpful for building polarization encoding MDI-QKD systems with better stability.

Fraction-order sideband generation in an optomechanical system.

We propose a scheme for generating a new kind of sideband, i.e., the fraction-order sideband, in an optomechanical system. In the conventional scheme of high-order sideband generation [Opt. Lett.38, 353 (2013)OPLEDP0146-959210.1364/OL.38.000353], the sideband interval has a minimum frequency limitation, which is equal to the mechanical frequency ωb, and this limits the precision of the sideband comb. With our proposed fraction-order sidebands, the sideband interval can break that limitation and reach ωb/n (n is an integer). The scheme we propose can be realized by driving the optomechanical system with three laser fields, including a control field (ωc) and two probe fields (ωp, ωf), in which the detuning between ωc and ωp is equal to the mechanical frequency ωb, while the detuning between ωc and ωf is equal to ωb/n. In this case, we find that not only the integer-order (high-order) sidebands, but also the fraction-order sidebands, and the sum and difference sidebands between the integer- and fraction-order sidebands, will appear in the output spectrum. Moreover, the sideband interval becomes ωb/n, and it can be decreased by increasing n. Our work paves the way to achieve a tunable optical frequency comb based on the optomechanical system.

Digital Simulation of Topological Matter on Programmable Quantum Processors.

Simulating the topological phases of matter in synthetic quantum simulators is a topic of considerable interest. Given the universality of digital quantum simulators, the prospect of digitally simulating exotic topological phases is greatly enhanced. However, it is still an open question how to realize the digital quantum simulation of topological phases of matter. Here, using common single- and two-qubit elementary quantum gates, we propose and demonstrate an approach to design topologically protected quantum circuits on the current generation of noisy quantum processors where spin-orbital coupling and related topological matter can be digitally simulated. In particular, a low-depth topological quantum circuit is performed on both the IBM and Rigetti quantum processors. In the experiments, we not only observe but also distinguish the 0 and π energy topological edge states by measuring the qubit excitation distribution at the output of the circuits.

Nonreciprocal transmission and fast-slow light effects in a cavity optomechanical system.

We study the nonreciprocal transmission and the fast-slow light effects in a cavity optomechanical system, in which the cavity supports a clockwise and a counter-clockwise circulating optical mode; both the modes are driven simultaneously by a strong pump field and a weak signal field. We find that the system reveals a nonreciprocal transmission of the signal fields when the intrinsic photon loss of the cavity is equal to the external coupling loss of the cavity. However, when the intrinsic photon loss is much less than the external coupling loss, the nonreciprocity about the transmission properties almost disappears, the nonreciprocity is shown in the group delay properties of the signal fields, and the system exhibits a nonreciprocal fast-slow light propagation phenomenon.

Improving the phase sensitivity of an SU(1,1) interferometer with photon-added squeezed vacuum light.

We study the phase sensitivity of an SU(1,1) interferometer from two aspects, i.e., the phase estimation determined by the error propagation formula and that by the quantum Cramér-Rao bound (QCRB). The results show that the phase sensitivity by using the intensity detection reaches the sub-shot-noise limit with a coherent state and an m-photon-added squeezed vacuum state (m-PA-SVS) as inputs. The phase sensitivity gradually approaches the Heisenberg limit for increasing m, and the ultimate phase precision improves with the increase of m. In addition, the QCRB can be saturated by the intensity detection with inputting the m-PA-SVS.

Quantum squeezing in a modulated optomechanical system.

Quantum squeezing, as a typical quantum effect, is an important resource for many applications in quantum technologies. Here we propose a scheme for generating quantum squeezing, including the ponderomotive squeezing and the mechanical squeezing, in an optomechanical system, in which the radiation-pressure coupling and the mechanical spring constant are modulated periodically. In this system, the radiation-pressure interaction can be enhanced remarkably by the modulation-induced mechanical parametric amplification. Moreover, the effective phonon noise can be suppressed completely by introducing a squeezed vacuum reservoir. This ultimately leads to that our scheme can achieve a controllable quantum squeezing. Numerical calculations show that our scheme is experimentally realizable with current technologies.

Entangling cavity optomechanical systems via a flying atom.

We propose a novel scheme to generate the entanglement between two cavity optomechanical systems (COMSs) via a flying two-level atom. We derive the analytical expressions for the generated entangled states. We find that there exist two processes for generating entanglement: one is the entanglement transfer between the two phonon-modes, and the other is the entanglement swapping-like process among the two photon-modes and the two phonon-modes. We analyze these two kinds of phenomena, respectively, by adjusting the distance between the two COMSs. Then we discuss the verification of the generated entangled states of the two COMSs, and analyze the decoherence of the generated entangled states. Finally, we discuss the experimental feasibility of our proposal.

Mechanical squeezing and photonic anti-bunching in a coupled two-cavity optomechanical system.

We propose a scheme for generating the squeezing of a mechanical mode and the anti-bunching of photonic modes in an optomechanical system. In this system, there are two photonic modes (the left cavity-mode and the right cavity-mode) and one mechanical mode. Both the left cavity-mode and the right cavity-mode are driven by two lasers, respectively. The power of the driving lasers and the detuning between them play a key role in generating squeezing of the mechanical mode. We find that the squeezing of the mechanical mode can be achieved even at a high temperature by increasing the power of the driving lasers. We also find that the cavity-modes can show photonic anti-bunching under suitable conditions.

Controllable optomechanically induced transparency and ponderomotive squeezing in an optomechanical system assisted by an atomic ensemble.

We propose a system for realizing controllable optomechanically induced transparency (OMIT) and ponderomotive squeezing. In this system, an atomic ensemble driven by an external optical field couples with the cavity field in a typical optomechanical cavity. When the cavity is driven by a coupling laser and a probe laser, we can produce a switch for the probe field and adjust the width of the transparency window flexibly by manipulating the coupling strength between the atomic ensemble and the external optical field. We also investigate the ponderomotive squeezing properties of the transmitted field by analyzing its spectrum. Interestingly, the coupling strength between the atomic ensemble and the cavity field plays an important role in controlling the squeezing properties and the squeezing spectrum presents distinct features at red-detuned and blue-detuned frequencies by adjusting the coupling strength.

Microwave field controlled slow and fast light with a coupled system consisting of a nanomechanical resonator and a Cooper-pair box.

We theoretically demonstrate an efficient method to control slow and fast light in microwave regime with a coupled system consisting of a nanomechanical resonator (NR) and a superconducting Cooper-pair box (CPB). Using the pump-probe technique, we find that both slow and fast light effects of the probe field can appear in this coupled system. Furthermore, we show that a tunable switch from slow light to fast light can be achieved by only adjusting the pump-CPB detuning from the NR frequency to zero. Our coupled system may have potential applications, for example, in optical communication, microwave photonics, and nonlinear optics.

Post-transplant lymphoproliferative disorders after allogeneic hematopoietic stem cell transplantation: a case report, meta-analysis, and systematic review.

BACKGROUND: Post-transplant lymphoproliferative disorders (PTLD) are rare but severe complications that occur after solid organ or allogeneic hematopoietic stem cell transplantations (allo-HSCT), with rapid progression and high mortality. Primary central nervous system (CNS)-PTLD are rarely recognized histo-pathologically. In addition, the diagnostic value of the Epstein-Barr virus (EBV) DNA copies in CNS-PTLD remains poorly understood. OBJECTIVES: We herein report a case of monomorphic EBV-associated CNS-PTLD (diffuse large B-cell lymphoma, DLBCL) after allo-HSCT and perform a meta-analysis to assess the efficacy of PTLD treatment strategies in recent years. METHODS: We present the case report covering clinical manifestations, diagnosis, treatment, and outcomes of a patient with primary CNS-PTLD. Additionally, we include a systematic review and meta-analysis of the clinical characteristics of 431 patients with PTLD after allo-HSCT. We evaluate the main treatment options and outcomes of PTLD management, including rituximab, chemotherapies, and autologous or human leukocyte antigen (HLA)-matched EBV-specific cytotoxic T lymphocyte infusion (EBV-CTLs)/donor lymphocyte infusion (DLI). RESULTS: The meta-analysis revealed an overall response rate of 69.0% for rituximab alone (95% CI: 0.47-0.84), 45.0% for rituximab plus chemotherapies (95% CI: 0.15-0.80), and 91.0% for rituximab plus EBV-CTLs/DLI (95% CI: 0.83-0.96). The complete response (CR) rate after treatments for PTLD was 67.0% (95% CI: 0.56-0.77). Moreover, the 6-month and 1-year overall survival (OS) rate was 64.0% (95% CI: 0.31-0.87) and 49.0% (95% CI: 0.31-0.68), respectively. CONCLUSIONS: This case highlighted the urgent need for effective, low-toxic treatment regimens for CNS-PTLD. Our meta-analysis suggested that rituximab combined with EBV-CTLs/DLI could be a favorable strategy for the management of PTLD after allo-HSCT.

Removal pathway quantification and co-metabolic mechanism evaluation of alkylphenols from synthetic wastewater by phenolic root exudates in the rhizosphere of Phragmites australis.

Phenolic root exudates (PREs) released from wetland plants are potentially effective for accelerating the biodegradation of alkylphenols, yet the inherent behavior is still unclear. In this study, two representative root exudates (REs), namely p-coumaric acid (PREs) and oxalic acid (non-PREs) were exogenously added as specific and non-specific co-metabolic substrates, respectively, to elucidate the quantification of each removal pathway and degradation mechanism of co-metabolism for alkylphenols (i.e. p-tert-butylphenol (PTBP)) from synthetic wastewater. The results showed that soil adsorption (31-37%), microbial degradation (27-37%), and plant uptake (16-41%) are the main removal pathways of PTBP by PREs in the Phragmites australis rhizosphere. Both REs enriched anaerobic functional community (anaerobic ammonium oxidation bacteria and denitrifying bacteria) and promoted the usage of PTBP as carbon source and/or electron donor. The activity of non-specific enzyme (polyphenol oxidase) was enhanced by RE which owning a significant positive correlation with bacterial abundance, whereas only PREs strengthened the activity of specific enzyme (monophenol oxidase) catalyzing the phenolic ring hydroxylation of PTBP followed by a dehydrogenation route. Moreover, exogenous PREs significantly improved the growth of degrading-related bacteria (Sphingomonas and Gemmatimonas), especially in unplanted soils with high activity of dioxygenase catalyzing the cleavage pathway of PTBP, instead of plant presence.

Abnormalities of bone marrow B cells and plasma cells in primary immune thrombocytopenia.

Primary immune thrombocytopenia (ITP) is an autoantibody-mediated hemorrhagic disorder in which B cells play an essential role. Previous studies have focused on peripheral blood (PB), but B cells in bone marrow (BM) have not been well characterized. We aimed to explore the profile of B-cell subsets and their cytokine environments in the BM of patients with ITP to further clarify the pathogenesis of the disease. B-cell subpopulations and their cytokine/chemokine receptors were detected by using flow cytometry. Plasma concentrations of cytokines/chemokines were measured by using enzyme-linked immunosorbent assay. Messenger RNA levels of B cell-related transcription factors were determined by using quantitative polymerase chain reaction. Regulatory B cell (Breg) function was assessed by quantifying their inhibitory effects on monocytes and T cells in vitro. Decreased proportions of total B cells, naive B cells, and defective Bregs were observed in patients with ITP compared with healthy controls (HCs), whereas an elevated frequency of long-lived plasma cells was found in BM of autoantibody-positive patients. No statistical difference was observed in plasmablasts or in short-lived plasma cells between patients with ITP and HCs. The immunosuppressive capacity of BM Bregs from patients with ITP was considerably weaker than HCs. An in vivo study using an active ITP murine model revealed that Breg transfusion could significantly alleviate thrombocytopenia. Moreover, overactivation of CXCL13-CXCR5 and BAFF/APRIL systems were found in ITP patient BM. Taken together, B-cell subsets in BM were skewed toward a proinflammatory profile in patients with ITP, suggesting the involvement of dysregulated BM B cells in the development of the disease.

The association between antinuclear antibody and response to rituximab treatment in adult patients with primary immune thrombocytopenia.

Background: Antinuclear antibodies (ANAs) can be detected in about 30% of patients with primary immune thrombocytopenia (ITP), yet their relationship with treatment response to rituximab remains elusive.Methods: we retrospectively reviewed the clinical records of hospitalized adult ITP patients who were treated with rituximab from three medical centers across China. Rituximab was given intravenously at 100 mg weekly for 4 weeks, or at a single dose of 375 mg/m2. All included patients had their ANAs tested before rituximab treatment.Results: A total of 287 patients fulfilled the inclusion criteria and were eligible for analysis. ANAs were positive in 98 (34.1%) of the included patients. The incidence of overall response and complete response (CR) in ANA-positive patients was significantly higher than that in ANA-negative patients (overall response: 76.5% vs. 55.0%, P < 0.001; CR: 46.9% vs. 29.1%, P = 0.003). However, sustained response (SR) rates in ANA-positive patients at 6, 12 and 24 months were all lower compared with ANA-negative patients (all P < 0.05). The overall duration of response (DOR) estimated by Kaplan-Meier analysis in ANA-negative patients was greater than that in ANA-positive patients (P < 0.001).Conclusion: ITP patients with positive ANA test were likely to achieve a better initial response to rituximab treatment, while their long-term outcome was unfavorable. Therefore, ANA test could be useful for predicting rituximab response in ITP.