Quantum networks play an extremely important role in quantum information science, with application to quantum communication, computation, metrology, and fundamental tests. One of the key challenges ...for implementing a quantum network is to distribute entangled flying qubits to spatially separated nodes, at which quantum interfaces or transducers map the entanglement onto stationary qubits. The stationary qubits at the separated nodes constitute quantum memories realized in matter while the flying qubits constitute quantum channels realized in photons. Dedicated efforts around the world for more than 20 years have resulted in both major theoretical and experimental progress toward entangling quantum nodes and ultimately building a global quantum network. Here, the development of quantum networks and the experimental progress over the past two decades leading to the current state of the art for generating entanglement of quantum nodes based on various physical systems such as single atoms, cold atomic ensembles, trapped ions, diamonds with nitrogen‐vacancy centers, and solid‐state host doped with rare‐earth ions are reviewed. Along the way, the merits are discussed and the potential of each of these systems toward realizing a quantum network is compared.
Quantum networks linking multiple remote quantum nodes consist of quantum memories served as stationary quantum nodes and flying photonic qubits served as quantum channels. This review summarizes and discusses the state of the art and future challenges for constructing quantum networks in various physical systems like single neutral atoms, cold atomic ensembles, trapped ions, NV centers, and rare‐earth‐ion doped solids.
An amorphous solid based on the Pd12L24 cage, namely aMOC-1, was constructed. The aMOC-1 can adsorb anionic dyes of different sizes rapidly and cationic dyes of a specific size. Thus, the ...time-dependent dye separation of anionic and cationic dyes from water was achieved. The good adsorption and separation performance of aMOC-1 is caused by the large cavities and the high positive Zeta potential of the material, which were created by the Pd12L24 metal-organic cages.
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•The idea of constructing amorphous solid based on MOC was put forward.•The adsorption of anionic dyes is rapidly that completely within 30 min.•The adsorption of cationic dye displays a size-selective adsorption.•A new mode for dye separation, namely time-dependent dye separation, is explored.
For the first time, an amorphous solid contains large cationic M12L24 metal–organic cage (MOC) based on Pd(II) and 3,5-di-pyridin-4-yl-benzaldehyde (L), namely aMOC-1, was constructed and characterized. Although it is an amorphous structure, regular cavity that created by MOC still exists in the solid and performs excellent dye adsorption and separation ability in water. The aMOC-1 can rapidly adsorb the anionic dyes including methyl orange (MO), fluorescein disodium salt (FS), acid fuchsin (AF) and methyl blue (MB) only in several minutes to about 30 min. The adsorption capacities for them are 359, 464, 116 and 150 mg/g, respectively. On the contrary, the adsorption rate of aMOC-1 towards cationic dyes is significantly slower than that of anionic dyes. The adsorption of cationic dyes shows a size-selectively behavior, in which the adsorption of rhodamine B (RhB) is more favorable than the other selected smaller or bigger cationic dyes. The adsorption capacity of RhB is up to 454 mg/g. According to the differences in the adsorption rates and capacities for different charged dyes, aMOC-1 displays diverse dye separation behaviors. It can selectively adsorb RhB from a mixed solution of MLB and RhB by size selectivity. Moreover, the selective separation of anionic and cationic dyes shows an interesting new time-dependence mode that the anionic dye can be selectively adsorbed from a mixed solution of anionic and cationic dyes by controlling the adsorption time. The good adsorption and separation performance of aMOC-1 is caused by the large cavity and the high positive Zeta potential of the material, which are created by the Pd12L24 metal-organic cages.
Mechanical resonators are promising systems for storing and manipulating information. To transfer information between mechanical modes, either direct coupling or an interface between these modes is ...needed. In previous works, strong coupling between different modes in a single mechanical resonator and direct interaction between neighboring mechanical resonators have been demonstrated. However, coupling between distant mechanical resonators, which is a crucial request for long-distance classical and quantum information processing using mechanical devices, remains an experimental challenge. Here, we report the experimental observation of strong indirect coupling between separated mechanical resonators in a graphene-based electromechanical system. The coupling is mediated by a far-off-resonant phonon cavity through virtual excitations via a Raman-like process. By controlling the resonant frequency of the phonon cavity, the indirect coupling can be tuned in a wide range. Our results may lead to the development of gate-controlled all-mechanical devices and open up the possibility of long-distance quantum mechanical experiments.
Abstract
Stellar white-light flares are believed to play an essential role in the physical and chemical properties of the atmosphere of the surrounding exoplanets. Here we report an optical ...monitoring campaign on the nearby flaring system EI Cnc carried out by the Ground-based Wide Angle Camera (GWAC) and its dedicated follow-up telescope. A superflare, coming from the brighter component EI CncA, was detected and observed, in which four components are required to properly model the complex decay light curve. The lower limit of flare energy in the
R
− band is estimated to be 3.3 × 10
32
erg. A total of 27 flares are additionally detected from the GWAC archive data with a total duration of 290 hr. The inferred cumulative flare frequency distribution follows a quite shallow power-law function with a slope of
β
= − 0.50 ± 0.03 over the energy range between 10
30
and 10
33
erg, which reinforces the trend that stars cooler than M4 show enhanced superflare activity. The flares identified in EI Cnc enable us to extend the
τ
–
E
relationship previously established in the white-light superflares of solar-type stars down to an energy as low as ∼10
30
erg (i.e., by 3 orders):
τ
∝
E
0.42±0.02
, which suggests a common flare mechanism for stars with a type from M to solar-like and implies an invariant of
B
1/3
υ
A
in the white-light flares.
Vibrational modes in mechanical resonators provide a promising candidate to interface and manipulate classical and quantum information. The observation of coherent dynamics between distant mechanical ...resonators can be a key step toward scalable phononbased applications. Here we report tunable coherent phonon dynamics with an architecture comprising three graphene mechanical resonators coupled in series, where all resonators can be manipulated by electrical signals on control gates. We demonstrate coherent Rabi oscillations between spatially separated resonators indirectly coupled via an intermediate resonator serving as a phonon cavity. The Rabi frequency fits well with the microwave burst power on the control gate. We also observe Ramsey interference, where the oscillation frequency corresponds to the indirect coupling strength between these resonators. Such coherent processes indicate that information encoded in vibrational modes can be transferred and stored between spatially separated resonators, which can open the venue of on-demand phonon-based information processing.
Abstract
Multi‐wavelength quantum light sources are extremely desired in establishing communication links among multiple users for realizing quantum networks. Despite recent impressive advances, ...developing such a quantum light source with high quality remains challenging. Here a multi‐wavelength quantum light source using a silicon nitride micro‐ring with a free spectral range of 200 GHz is demonstrated. The generation of eight‐wavelength‐paired photon pairs is ensured in a wavelength range of 25.6 nm. With device optimization and noise‐rejecting filters, this source enables the generation of heralded single‐photons at a rate of 62 kHz with and the generation of energy‐time entangled photons with a visibility of in the Franson interferometer. These results, at room temperature and telecom wavelength, in a CMOS‐compatible platform, represent an important step toward integrated quantum photonic devices, which pave the way for realizing a large‐scale quantum network.
Metal-organic frameworks (MOFs) with high chemical stability in solution are of great interest and have potential for the removal of environmental contaminants. Herein, a MOF (SCNU-Z4) possessing a ...cage cavity and channels based on Cu(
ii
) and a bifunctional tripodal nitrogen-donor ligand has been constructed and used to capture I
2
molecules and hazardous dyes in solution. The truncated octahedron cage in SCNU-Z4 is similar to that in the well-known M-BTT (H
3
BTT = 1,3,5-benzenetristetrazolate) MOFs but is composed of both trinuclear and tetranuclear SBUs. The BET test showed that both micropores and mesopores were observed in the crystal sample, and it showed potential ability for CO
2
/N
2
separation. This MOF shows high stability in aqueous solution with a pH ranging from 3 to 11 and in various organic solvents. Due to the porous framework, uncoordinated N donor and hydrolytic stability, the I
2
and aqueous-phase dye adsorption applications of SCNU-Z4 were explored. The results indicate that SCNU-Z4 can capture I
2
in both cyclohexane and aqueous solutions, and the absorption capacity is approximately 237 mg g
−1
and 332 mg g
−1
, respectively. Dye adsorption experiments showed that it can absorb both anionic and cationic dyes. The adsorption of a mixed MO & MLB solution showed a synergistic effect. The separation of MLB & RhB and MLB & CR can be achieved by size-dependent and kinetic-dependent modes, respectively. SCNU-Z4 showed the best adsorption towards CR. This MOF exhibits a high adsorption capacity of 1200 mg g
−1
, which is among the best for MOFs, and the adsorption kinetics are faster than those of other selected dyes. A mechanistic study revealed that the high capacity can be attributed to the hydrogen bonding and π π interactions between the SCNU-Z4 host and CR guest molecules. Unexpectedly, SCNU-Z4 also showed a moderate adsorption capacity for the large AB dye molecule. The adsorption capacity of SCNU-Z4 for AB reached 221 mg g
−1
, which is far beyond its self-decomposition. The adsorption may be due to the surface adsorption and mesopores that are generated from the defects of SCNU-Z4. The good adsorption performance of SCNU-Z4 is caused by the cage-like framework, diverse pores and interaction sites.
A metal-organic framework (SCNU-Z4) with high chemical stability in water and common organic solvents showed ability for iodine and dye adsorption.
Cationic framework materials capable of removing anionic pollutants from wastewater are highly desirable but relatively rarely reported. Herein, a cationic MOF (SCNU-Z1-Cl) possessing tubular ...channels with diameter of 1.5 nm based on Ni(II) and a nitrogen-containing ligand has been synthesized and applied to capture hazardous anionic contaminants from water. The SCNU-Z1-Cl exhibits high BET surface area of 1636 m2/g, and shows high hydrolytically stability in pH range from 4 to 10. Owing to the large tubular channels and the uncoordinated anions in the framework, the aqueous-phase anion-exchange applications of SCNU-Z1-Cl were explored with environmentally toxic oxo-anions including CrO4 2–, Cr2O7 2–, MnO4 –, and ReO4 –, and organic dyes. The adsorption of oxoanions exhibits high uptake kinetics and the adsorption capacities of CrO4 2–, Cr2O7 2–, MnO4 –, and ReO4 – are 126, 241, 292, and 318 mg/g, respectively, which were some of the highest values in the field of MOF/COF. In additional, the selectively is high when other concurrent anions are exist. The anionic dyes with different sizes including methyl orange, acid orange A, congo red, as well as methyl blue can be adsorbed by SCNU-Z1-Cl in few minutes to about 1 h. The adsorption capacities for them are 285, 180, 585, and 262 mg/g, respectively. In contrast, the adsorption kinetics for catinionic dyes with different sizes is obviously lower and exhibit a size-selectively adsorption that only cationic dye with suitable size (rhodamine B) can be adsorbed by SCNU-Z1-Cl. Consequently, SCNU-Z1-Cl can sepearate organic dyes in three different modes: size-dependent, charge-dependent, and kinetics-dependent selective adsorption. The excellent adsorption and separation properties of SCNU-Z1-Cl is attribute to the cationic framework, large tubular channel, as well as the high positive Zeta potential.
We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing ...rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.
Coupling an electromechanical resonator with carbon-nanotube quantum dots is a significant method to control both the electronic charge and the spin quantum states. By exploiting a novel ...microtransfer technique, we fabricate two separate strongly coupled and electrically tunable mechanical resonators for the first time. The frequency of the two resonators can be individually tuned by the bottom gates, and in each resonator, the electron transport through the quantum dot can be strongly affected by the phonon mode and vice versa. Furthermore, the conductance of either resonator can be nonlocally modulated by the other resonator through phonon–phonon interaction between the two resonators. Strong coupling is observed between the phonon modes of the two resonators, where the coupling strength larger than 200 kHz can be reached. This strongly coupled nanotube electromechanical resonator array provides an experimental platform for future studies of the coherent electron–phonon interaction, the phonon-mediated long-distance electron interaction, and entanglement state generation.
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