We report on a quantum interference experiment to probe the coherence between two photons coming from non degenerate photon pairs at telecom wavelength created in spatially separated sources. The two photons are mixed on a beam splitter and we observe a reduction of up to 84% in the coincidence count rate when the photons are made indistinguishable. This experiment constitutes an important step towards the realization of quantum teleportation and entanglement swapping with independent sources.
Multiparticle entangled states, essential ingredients for modern quantum technologies, are routinely generated in experiments of atomic Bose-Einstein condensates (BECs). However, the entanglement in ultracold interacting Fermi gases has not been yet exploited. In this work, by using an ansatz of composite bosons, we show that many-particle entanglement between two fermionic ensembles localized in spatially separated modes can be generated by splitting an ultracold interacting Fermi gas in the (molecular) BEC regime. This entanglement relies on the fundamental fermion exchange symmetry of molec…
The quantum superposition principle implies that a particle entering an interferometer evolves by simultaneously taking both arms. If a non-destructive, minimally-disturbing interaction coupling a particle property to a pointer is implemented on each arm while maintaining the path superposition, quantum theory predicts that, for a fixed state measured at the output port, certain particle properties can be associated with only one or the other path. Here we report realization of this prediction through joint observation of the spatial and polarization degrees of freedom of a single photon in th…
Wave and particle are two fundamental properties of Nature. The wave-particle duality has indicated that a quantum object may exhibit the behaviours of both wave and particle, depending upon the circumstances of the experiment. The major significance of wave-particle duality has led to a fundamental equation in quantum mechanics, the Schr{\" o}dinger equation. At present, the principle of wave-particle duality has been deeply rooted in people's hearts. This gives rise to a common sense perception that wave property and particle property coexist simultaneously in a quantum entity, and these two…
We consider a monoenergetic beam of moving charged particles interacting with two separated oscillating electric fields. Time-periodic linear potential is assumed to model the light-particle interaction using a nonrelativistic, quantum mechanical description based on Gordon-Volkov states. Applying Floquet theory, we calculate transmission probabilities as a function of the laser field parameters. The transmission resonances in this Ramsey-like setup are interpreted as if they originated from a corresponding static double-potential barrier with heights equal to the ponderomotive potential resul…
Superconducting circuits are a strong contender for realizing quantum computing systems, and are also successfully used to study quantum optics and hybrid quantum systems. However, their cryogenic operation temperatures and the current lack of coherence-preserving microwave-to-optical conversion solutions have hindered the realization of superconducting quantum networks either spanning different cryogenics systems or larger distances. Here, we report the successful operation of a cryogenic waveguide coherently linking transmon qubits located in two dilution refrigerators separated by a physica…
We propose a method to witness entanglement between two continuous-variable systems in a Gaussian state. Its key ingredient is a local lossy state transfer from the original spatially separated systems onto two spatially separated qubits. The qubits are initially in a pure product state, therefore by detecting entanglement between the qubits we witness entanglement between the two original systems. This method greatly simplifies entanglement witnessing in complex systems.
Parallel distributed quantum gates for dual-species quantum emitters
MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing, School of Physics, Nanjing University of Science and Technology（南京理工大学物理学院）；Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University（亚当·密茨凯维奇大学物理学院自旋电子学与量子信息研究所）；Center for Quantum Computing, RIKEN（理化学研究中心量子计算中心）；Engineering Research Center of Semiconductor Device Optoelectronic Hybrid Integration in Jiangsu Province（江苏省半导体器件光电混合集成工程研究中心）；Physics Department, The University of Michigan（密歇根大学物理系）
On-chip Dicke-type magnon polaritons in the ultrastrong coupling regime via spatially separated nanomagnets
Kyoto University（京都大学）；Center for Spintronics Research Network, Institute for Chemical Research, Kyoto University（京都大学化学研究所在旋电子学研究网络中心）；Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften（巴伐利亚科学院瓦尔特-迈斯纳研究所）；Technical University of Munich, TUM School of Natural Sciences, Physics Department（慕尼黑工业大学自然科学学院物理系）；Osaka Metropolitan University（大阪公立大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）
In a quantum sense, vacuum is not an empty void but full of virtual particles (fields). It may have long-range properties, be altered, and even undergo phase transitions. It is suggested that long-range properties of a quantum vacuum may be probed by distributing matter over a large spatial volume. Here, we study a simplest example of such, i.e., two uniformly accelerated Unruh-DeWitt detectors which are spatially separated, and examine the inter-detector interaction energy arising from the coupling between the detectors and fluctuating fields to see if novel phenomena related to the long-rang…
Locality plays a fundamental role in quantum computation but also severely restricts our ability to store and process quantum information. We argue that this restriction may be unwarranted and re-examine quantum error correcting codes. We proceed to introduce new defects on the surface code called wormholes. These novel defects entangle two spatially separated sectors of the lattice. When anyonic excitations enter the mouth of a wormhole, they emerge through the other mouth. Wormholes thus serve to connect two spatially separated sectors of a flat, $2$D lattice. We show that these defects are …
The violation of a Bell inequality is a striking demonstration of how quantum mechanics contradicts local realism. Although the original argument was presented with a pair of spin 1/2 particles, so far Bell inequalities have been shown to be violated using entangled pairs of photons, with recent measurements closing all possible loopholes in such a scheme. Equivalent demonstrations using massive particles have proven to be much more challenging, generally relying on post-selection of data or measuring an entanglement witness that relies on quantum mechanics. Here, we use a collision between tw…
Besides striving to assemble more and more qubits in a single monolithic quantum device, taking a modular design strategy may mitigate numerous engineering challenges for achieving large-scalable quantum processors with superconducting qubits. Nevertheless, a major challenge in the modular quantum device is how to realize high-fidelity entanglement operations on qubits housed in different modules while preserving the desired isolation between modules. In this work, we propose a conceptual design of a modular quantum device, where nearby modules are spatially separated by centimeters. In princi…
We reconsider the all-optical homodyne-measurement based experimental schemes that aim to reveal Bell nonclassicality of a single photon, often termed `nonlocality'. We focus on the schemes put forward by Tan, Walls and Collett (TWC, 1991) and Hardy (1994). In the light of our previous work the Tan, Walls and Collett setup can be described by a precise local hidden variable model, hence the claimed nonclassicality of this proposal is apparent, whereas the nonclassicality proof proposed by Hardy is impeccable. In this work we resolve the following problem: which feature of the Hardy's approach …
Graduate School of Advanced Science and Engineering, Hiroshima University（广岛大学先进理工学研究科）；School of Computing, Newcastle University（纽卡斯尔大学计算机学院）；Quantum Engineering Technology Laboratories, Department of Electrical and Electronic Engineering, University of Bristol（布里斯托大学电气电子工程系量子工程技术实验室）
Large-scale quantum computers will require quantum gate operations between widely separated qubits. A method for implementing such operations, known as quantum gate teleportation (QGT), requires only local operations, classical communication, and shared entanglement. We demonstrate QGT in a scalable architecture by deterministically teleporting a controlled-NOT (CNOT) gate between two qubits in spatially separated locations in an ion trap. The entanglement fidelity of our teleported CNOT is in the interval [0.845, 0.872] at the 95% confidence level. The implementation combines ion shuttling wi…
Asymmetric quantum telecloning of d-level systems and broadcasting of entanglement to different locations using the "many-to-many" communication protocol
