Couplers for Non-Locality Swapping

Locality-aware Qubit Routing for the Grid Architecture

Due to the short decohorence time of qubits available in the NISQ-era, it is essential to pack (minimize the size and or the depth of) a logical quantum circuit as efficiently as possible given a sparsely coupled physical architecture. In this work we introduce a locality-aware qubit routing algorithm based on a graph theoretic framework. Our algorithm is designed for the grid and certain "grid-like" architectures. We experimentally show the competitiveness of algorithm by comparing it against the approximate token swapping algorithm, which is used as a primitive in many state-of-the-art quant…

Delayed - Choice Entanglement - Swapping with Vacuum-One Photon Quantum States

We report the experimental realization of a recently discovered quantum information protocol by Asher Peres implying an apparent non-local quantum mechanical retrodiction effect. The demonstration is carried out by applying a novel quantum optical method by which each singlet entangled state is physically implemented by a two-dimensional subspace of Fock states of a mode of the electromagnetic field, specifically the space spanned by the vacuum and the one photon state, along lines suggested recently by E. Knill et al., Nature 409, 46 (2001) and by M. Duan et al., Nature 414, 413 (2001). The s…

Experimental demonstration of nonbilocality with truly independent sources and strict locality constraints

Entanglement swapping entangles two particles that have never interacted[1], which implicitly assumes that each particle carries an independent local hidden variable, i.e., the presence of bilocality[2]. Previous experimental studies of bilocal hidden variable models did not fulfill the central requirement that the assumed two local hidden variable models must be mutually independent and hence their conclusions are flawed on the rejection of local realism[3-5]. By harnessing the laser phase randomization[6] rising from the spontaneous emission to the stimulated emission to ensure the independe…

Quantum non-locality, causality and mistrustful cryptography

Here we propose a general relativistic quantum framework for cryptography that exploits the fascinating connection of quantum non-locality and special theory of relativity with cryptography. The underlying principle of unconditional security is causality and two-fold quantum non-local correlations: first entanglement swapping and then teleportation over causally independent entangled systems. We show that the proposed framework has following remarkable and novel features in mistrustful cryptography: (i) It helps in defining a new notion of oblivious transfer where both the data transferred and…

Experimental refutation of real-valued quantum mechanics under strict locality conditions

Physicists describe nature using mathematics as the natural language, and for quantum mechanics, it prefers to use complex numbers. However, whether complex numbers are really necessary for the theory has been debated ever since its birth. Recently, it has been shown that a three-party correlation created in entanglement swapping scenarios comprising independent states and measurements cannot be reproduced using only real numbers. Previous experiments have conceptually supported the predication, yet not satisfying the independent state preparations and measurements simultaneously. Here, we imp…

网络中的真正Bell局域性与非局域性

Genuine Bell locality and nonlocality in the networks

本文研究网络中的真正Bell局域性与非局域性，提出涉及更多关联子的线性和非线性Bell型不等式，利用Pauli算符设计Bell测试并证明其最大违背，最后演示纠缠交换替代联合测量。

利用硅集成光子学实现芯片间超纠缠分发与纠缠纯化

Chip-to-chip hyperentanglement distribution and entanglement purification using silicon integrated photonics

该研究首次在集成硅芯片间实现偏振-空间超纠缠分发，并通过消耗空间自由度完成纠缠纯化，弥补了片上量子中继器的关键环节。

Entanglement Between Photons that have Never Coexisted

The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving, can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the non-locality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spatial separation, but also with temporal separation. Here we demonstrate these principles by generating and fully characterizing an…

弱相互作用量子系统的温度均匀局部性估计

Uniform-in-temperature locality estimates for weakly interacting quantum systems

本文证明弱相互作用量子系统在任意温度下均满足相关函数的指数衰减和局部不可区分性，利用低温簇展开和量子概率交换技巧。

Particle exchange in post-quantum theories

In quantum theory, particles in three spatial dimensions come in two different types: bosons or fermions, which exhibit sharply contrasting behaviours due to their different exchange statistics. Could more general forms of probabilistic theories admit more exotic types of particles? Here, we propose a thought experiment to identify more exotic particles in general post-quantum theories. We consider how in quantum theory the phase introduced by swapping indistinguishable particles can be measured. We generalise this to post-quantum scenarios whilst imposing indistinguishability and locality pri…

最简单因果网络中的量子非经典性

A minimal example of quantum non-classicality without freedom of choice

本文研究了最简单因果网络中量子非经典性的实现，展示了无需局部性假设的实验可行性，并通过干预提高噪声鲁棒性。