Entanglement Routers Using Macroscopic Singlets

Generation of macroscopic singlet states in a cold atomic ensemble

We report the generation of a macroscopic singlet state in a cold atomic sample via quantum non-demolition (QND) measurement induced spin squeezing. We observe 3 dB of spin squeezing and detect entanglement of up to $5.5\times10^5 $ atoms with $5σ$ statistical significance using a generalized spin squeezing inequality. The degree of squeezing implies at least 50% of the atoms have formed singlets, while the response to a magnetic field gradient indicates entanglement bonds at all length scales, a characteristic of quantum spin liquids.

Macroscopic singlet states for gradient magnetometry

We present a method for measuring magnetic field gradients with macroscopic singlet states realized with ensembles of spin-j particles. While the singlet state is completely insensitive to homogeneous magnetic fields, the variance of its collective spin components is highly sensitive to field gradients. We compute the dynamics of this variance analytically for a chain of spins and also for an ensemble of particles with a given density distribution. We find an upper bound on how precisely the field gradient can be estimated from the measured data. Based on our calculations, differential magneto…

Generation of macroscopic singlet states in atomic ensembles

We study squeezing of the spin uncertainties by quantum non-demolition (QND) measurement in non-polarized spin ensembles. Unlike the case of polarized ensembles, the QND measurements can be performed with negligible back-action, which allows, in principle, perfect spin squeezing as quantified by [G. Toth et al., Phys. Rev. Lett. 99, 250405 (2007)]. The generated spin states approach many-body singlet states, and contain a macroscopic number of entangled particles, even when individual spin is large. We introduce the Gaussian treatment of unpolarized spin states and use it to estimate the achie…

在InAsP量子点纳米线中的合成自旋一链中利用宏观单态-三态量子比特实现双量子比特门

Two qubit gate with macroscopic singlet-triplet qubits in synthetic spin-one chains in InAsP quantum dot nanowires

本文提出在InAsP量子点纳米线的合成自旋一链中，利用宏观拓扑保护单态-三态量子比特实现双量子比特门的理论，通过精确对角化和MPS工具验证低能行为，并演示了两种高精度门生成方法。

Macroscopic Bell States and the Higher-Order Degree of Polarization

We study polarization properties of the macroscopic analogues of two-photon Bell states. The effect of hidden polarization, i.e., polarization in the second (and higher) orders in the intensity is observed for the triplet states while the singlet one is demonstrated to be nearly unpolarized at least up to the fourth order. The arbitrary-order degree of polarization is introduced and applied to the macroscopic Bell states.

相干光子的宏观单态、三重态和色荷态

Macroscopic Singlet, Triplet, and Colour-Charged States of Coherent Photons

本研究实验展示了利用常见光学元件构建相干光子量子态的旋转生成元，实现了SU(3)、SU(4)及单态、三重态等宏观量子态，并验证了投影行为。