In the absence of decay, the conditional dynamics for an open system is often describable by a non-Hermitian Hamiltonian. This study investigates spin squeezing (SS) in a non-Hermitian one-axis twisting (OAT) model. Somewhat surprisingly, SS close to the limit of Hermitian two-axis counter twisting (TACT) Hamiltonian is achievable for some parameters, which significantly improves upon the optimal value realizable by the Hermitian OAT model. The drawback is like with all conditional schemes, it takes on average longer time to evolve into a steady state, and the probability of no decay or success decreases as the number of atoms (spins) increases. The result above for the steady-state SS in a non-Hermitian OAT Hamiltonian is thus limited to small systems. For other parameter regimes, however, desirable SS arrives dynamically before a steady state is achieved, with a greatly shortened evolution time and enhanced probability of success, while still remains significantly improved over the limit of Hermitian OAT.In the absence of decay, the conditional dynamics for an open system is often describable by a non-Hermitian Hamiltonian. This study investigates spin squeezing (SS) in a non-Hermitian one-axis twisting (OAT) model. Somewhat surprisingly, SS close to the limit of Hermitian two-axis counter twisting (TACT) Hamiltonian is achievable for some parameters, which significantly improves upon the optimal value realizable by the Hermitian OAT model. The drawback is like with all conditional schemes, it takes on average longer time to evolve into a steady state, and the probability of no decay or success decreases as the number of atoms (spins) increases. The result above for the steady-state SS in a non-Hermitian OAT Hamiltonian is thus limited to small systems. For other parameter regimes, however, desirable SS arrives dynamically before a steady state is achieved, with a greatly shortened evolution time and enhanced probability of success, while still remains significantly improved over the limit of Hermitian OAT.

arXiv:1504.01984Physical Review ASep 15, 201521 citations

Quantum spin squeezing

Jian Ma, Xiaoguang Wang, C. P. Sun +1 more

arXiv:1011.2978Physics ReportsSep 1, 2011846 citations

Near-optimal two-mode spin squeezing via feedback

Dominic William Berry, Barry C. Sanders

We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode spin squeezed states obtained via this feedback are optimal for $j=1/2$ and are very close to optimal for $j>1/2.$ In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single-mode case.We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode spin squeezed states obtained via this feedback are optimal for $j=1/2$ and are very close to optimal for $j>1/2.$ In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single-mode case.

arXiv:quant-ph/0203081Physical Review AJul 25, 200220 citations

Heisenberg operator approach for spin squeezing dynamics

Aranya B. Bhattacherjee, Deepti Sharma, Axel Pelster

arXiv:1605.02274The European Physical Journal DDec 1, 20174 citations

Spin Squeezing of Superposition

Song-Song Li

International Journal of Theoretical PhysicsNov 30, 201016 citations

Sensitive detection of entanglement in exciton-polariton condensates via spin squeezing

Jingyan Feng, Ebubechukwu O. Ilo-Okeke, Alexey N. Pyrkov +2 more

We propose a method of generating and detecting entanglement via spin squeezing in an exciton-polariton condensate. Spin squeezing is a sensitive detector of entanglement because any squeezing below shot noise implies entanglement. In our scheme, two polariton spin species are resonantly pumped, forming a particle number fluctuating effective spin. The naturally occurring nonlinear interactions between the polaritons produce an effective one-axis squeezing interaction, which drives the system toward a spin-squeezed state at steady-state. We investigate the squeezing level that is attainable at the steady state for realistic experimental parameters and show the favorable parameters for strong squeezing. The amount of squeezing tends to improve with larger pumping, due to the bosonic enhancement of the one-axis twisting Hamiltonian. Using number-fluctuating versions of the Wineland squeezing criterion and optimal spin inequalities, we show how multipartite entanglement can be detected.We propose a method of generating and detecting entanglement via spin squeezing in an exciton-polariton condensate. Spin squeezing is a sensitive detector of entanglement because any squeezing below shot noise implies entanglement. In our scheme, two polariton spin species are resonantly pumped, forming a particle number fluctuating effective spin. The naturally occurring nonlinear interactions between the polaritons produce an effective one-axis squeezing interaction, which drives the system toward a spin-squeezed state at steady-state. We investigate the squeezing level that is attainable at the steady state for realistic experimental parameters and show the favorable parameters for strong squeezing. The amount of squeezing tends to improve with larger pumping, due to the bosonic enhancement of the one-axis twisting Hamiltonian. Using number-fluctuating versions of the Wineland squeezing criterion and optimal spin inequalities, we show how multipartite entanglement can be detected.

Physical Review AJul 30, 20219 citations

j=1/2

and are very close to optimal for

j>1/2.

In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single-mode case.