Deriving mixed state of light field by partial tracing pure state in higher dimension

• Published in: Physica A Vol. 623; p. 128809
• Main Authors: Wan, Zhi-Long, Yuan, Hong-Chun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2023
• Subjects: New density operator; Partial trace; Wigner function; New density operator; Partial trace; Wigner function
• ISSN: 0378-4371; 1873-2119
• DOI: 10.1016/j.physa.2023.128809

In this paper, we show that by partial tracing the pure state in higher dimension one can deduce the mixed state of light field. In this paper the pure state in higher dimension is a three-mode squeezed state S23σS31τ000000S31−1τS23−1σ, while the mixed state’s density operator is sech2σsech2τea2†a3†tanhσsech2σtanh2τa3†a30220ea2a3tanhσ, which involves both squeezing and chaotic properties of optical field. We further explain how such kind of light field can be generated by  passing a two-mode squeezed light though a single-mode dissipative channel, its Wigner function is discussed by using the coherent state representation. Our work provides an important method, which can be used to theoretically find more optical fields in quantum communication and quantum optics.