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arXiv 2202.08607quant-phcond-mat.quant-gascond-mat.str-el
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源自连续对称性自发破缺的可扩展自旋压缩

Scalable spin squeezing from spontaneous breaking of a continuous symmetry

Tommaso Comparin, Fabio Mezzacapo, Martin Robert-de-Saint-Vincent, Tommaso Roscilde

备注：
5+3 pages, 3+6 figures - v2 (2025): a mistake was fixed in Fig. 7 and in its discussion
发表信息：
Phys. Rev. Lett. 129, 113201 (2022)
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AI总结：

针对连续对称量子自旋模型，研究证明通过绝热过程利用自发对称性破缺可制备可扩展的强自旋压缩态，给出其不确定度标度与制备时间特性，为量子计量等场景的态制备提供新方案。

摘要：

自发对称性破缺（SSB）是哈密顿量平衡态的一种性质：在热力学极限下，即便与序参量耦合的外场被绝热关闭，系统仍能保留有限的序参量平均值。针对具有连续对称性的量子自旋模型，我们证明该绝热过程还会伴随对称性生成元——即沿对称轴方向的集体自旋分量——的涨落被抑制。在S=1/2自旋或量子比特系统中，单方向涨落抑制与横向磁化保留的共同作用会产生自旋压缩，这是量子态备受关注的性质，可用于纠缠探测与量子计量。我们聚焦于自发破缺U(1)（甚至SU(2)）对称性的XXZ模型，证明绝热制备的态具有接近最小的自旋不确定度；利用这些态能实现的最小相位不确定度随自旋数N的标度关系为N^{-3/4}；达到该标度所需的绝热制备时间与N呈线性标度关系。我们的发现为在包括光晶格钟在内的各类量子多体装置中绝热制备强自旋压缩态开辟了路径。

英文摘要：

Spontaneous symmetry breaking (SSB) is a property of Hamiltonian equilibrium states which, in the thermodynamic limit, retain a finite average value of an order parameter even after a field coupled to it is adiabatically turned off. In the case of quantum spin models with continuous symmetry, we show that this adiabatic process is also accompanied by the suppression of the fluctuations of the symmetry generator -- namely, the collective spin component along an axis of symmetry. In systems of $S=1/2$ spins or qubits, the combination of the suppression of fluctuations along one direction and of the persistence of transverse magnetization leads to spin squeezing -- a much sought-after property of quantum states, both for the purpose of entanglement detection as well as for metrological uses. Focusing on the case of XXZ models spontaneously breaking a U(1) (or even SU(2)) symmetry, we show that the adiabatically prepared states have nearly minimal spin uncertainty; that the minimum phase uncertainty that one can achieve with these states scales as $N^{-3/4}$ with the number of spins $N$; and that this scaling is attained after an adiabatic preparation time scaling linearly with $N$. Our findings open the door to the adiabatic preparation of strongly spin-squeezed states in a large variety of quantum many-body devices including e.g. optical lattice clocks.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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