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We introduce a generalised input-output formalism that accurately describes realistic, non-unitary interferometers, including losses due to velocity selectivity and scattering into undesired momentum states. This formalism is applied to evaluate the performance of one-axis twisted spin-squeezed states in improving phase sensitivity. Our results show that by carefully optimising the parameters of the Bragg beam splitters and controlling the degree of squeezing, it is possible to improve the sensitivity of the interferometer by several dB with respect to the standard quantum limit despite realistic levels of losses in light pulse operations. However, the analysis also highlights the challenges associated with achieving these improvements in practice, most notably the impact of finite temperature on the benefits of entanglement. The results suggest ways of optimising interferometric setups to exploit quantum entanglement under realistic conditions, thereby contributing to advances in precision metrology with atom interferometers.<\/jats:p>","DOI":"10.22331\/q-2026-06-01-2122","type":"journal-article","created":{"date-parts":[[2026,6,1]],"date-time":"2026-06-01T07:53:49Z","timestamp":1780300429000},"page":"2122","update-policy":"https:\/\/doi.org\/10.22331\/q-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Squeezing Enhancement in Lossy Multi-Path Atom Interferometers"],"prefix":"10.22331","volume":"10","author":[{"given":"Julian","family":"G\u00c3\u00bcnther","sequence":"first","affiliation":[{"name":"Institute for Theoretical Physics, Leibniz Universit\u00e4t Hannover, Appelstra\u00dfe 2, 30167 Hannover, Germany"},{"name":"Institute of Quantum Optics, Leibniz Universit\u00e4t Hannover, Welfengarten 1, 30167 Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jan-Niclas","family":"Kirsten-Siem\u00c3\u009f","sequence":"additional","affiliation":[{"name":"Institute of Quantum Optics, Leibniz Universit\u00e4t Hannover, Welfengarten 1, 30167 Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Naceur","family":"Gaaloul","sequence":"additional","affiliation":[{"name":"Institute of Quantum Optics, Leibniz Universit\u00e4t Hannover, Welfengarten 1, 30167 Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Klemens","family":"Hammerer","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Theoretische Physik, Universit\u00e4t Innsbruck, 6020 Innsbruck, Austria"},{"name":"Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, 6020 Innsbruck, Austria"},{"name":"Institute for Theoretical Physics, Leibniz Universit\u00e4t Hannover, Appelstra\u00dfe 2, 30167 Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"9598","published-online":{"date-parts":[[2026,6,1]]},"reference":[{"key":"0","doi-asserted-by":"publisher","unstructured":"D. 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