Unitary reformulation of the thermofield double state and limits of cyclic multi-mode squeezing
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| Format: | Preprint |
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2025
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| _version_ | 1866909711999172608 |
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| author | Azizi, Arash |
| author_facet | Azizi, Arash |
| contents | We investigate the structure and uniqueness of squeezed vacuum states defined by annihilation conditions of the form $(a - αa^\dagger)|ψ\rangle = 0$ and their multimode generalizations, with applications to the Thermofield Double (TFD) state in quantum field theory. For $N=1$ and $N=2$, we demonstrate that these conditions uniquely define the single- and two-mode squeezed vacua, generated by unitary squeezing operators. A key result is the unitary reformulation of the TFD state, expressed as a product of two-mode squeezing operators, ensuring invertibility and resolving the non-unitary paradox in the Minkowski--Rindler vacuum correspondence. Extending to cyclic annihilation conditions $(a_i - α_i a_{i+1}^\dagger)|ψ\rangle = 0$ with $a_{N+1} \equiv a_1$, we find that non-trivial squeezed states exist only for $N=2$. For $N > 2$, we establish a no-go theorem, proving no normalizable, non-trivial solutions exist, revealing a fundamental limit on cyclic multi-mode entanglement. These results highlight the bipartite nature of TFD-like entanglement and constrain multipartite generalizations in multi-region quantum field theories. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_09654 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Unitary reformulation of the thermofield double state and limits of cyclic multi-mode squeezing Azizi, Arash Quantum Physics High Energy Physics - Theory We investigate the structure and uniqueness of squeezed vacuum states defined by annihilation conditions of the form $(a - αa^\dagger)|ψ\rangle = 0$ and their multimode generalizations, with applications to the Thermofield Double (TFD) state in quantum field theory. For $N=1$ and $N=2$, we demonstrate that these conditions uniquely define the single- and two-mode squeezed vacua, generated by unitary squeezing operators. A key result is the unitary reformulation of the TFD state, expressed as a product of two-mode squeezing operators, ensuring invertibility and resolving the non-unitary paradox in the Minkowski--Rindler vacuum correspondence. Extending to cyclic annihilation conditions $(a_i - α_i a_{i+1}^\dagger)|ψ\rangle = 0$ with $a_{N+1} \equiv a_1$, we find that non-trivial squeezed states exist only for $N=2$. For $N > 2$, we establish a no-go theorem, proving no normalizable, non-trivial solutions exist, revealing a fundamental limit on cyclic multi-mode entanglement. These results highlight the bipartite nature of TFD-like entanglement and constrain multipartite generalizations in multi-region quantum field theories. |
| title | Unitary reformulation of the thermofield double state and limits of cyclic multi-mode squeezing |
| topic | Quantum Physics High Energy Physics - Theory |
| url | https://arxiv.org/abs/2505.09654 |