Entanglement and Wigner Function Negativity of Multimode Non-Gaussian States
The advent of quantum technologies mandates a thorough understanding of quantum states in various platforms, with optical setups emerging as potential key players due to their resilience against decoherence and ability to achieve high clock rates. This paper strategically investigates multimode non-Gaussian states generated through mode-selective photon addition and subtraction, pivotal processes for realizing optical continuous-variable quantum information protocols.
The core focus is on deriving an analytical expression for the Wigner function of multimode quantum states produced by the addition or subtraction of single photons. A significant accomplishment here is the derivation of a practical condition for Wigner function negativity, which is essential for potential quantum advantages.
Mode-selective operations in multimode scenarios pose considerable challenges. The authors utilize correlation functions, typically employed in quantum statistical mechanics, alongside quantum optics tools to overcome these complexities. They present a comprehensive analysis of entanglement and negativity properties in multimode contexts, emphasizing the importance of non-Gaussian operations for achieving quantum advantage over classical simulations of Gaussian states.
The paper outlines the exact expression of Wigner functions after the addition or subtraction of a single photon from a multimode Gaussian state, demonstrating its elegance and utility in quantifying non-Gaussian characteristics. A key finding is the condition for Wigner function negativity—a crucial property for quantum information applications—which differentiates between photon addition, where negativity is inherent, and photon subtraction, where mode-selectivity dictates success.
Photon addition and subtraction are scrutinized for their ability to entangle multiple modes. For mixed Gaussian states, the coherence of mode-selective photon processes is dissected, revealing that inherent entanglement arises when photons are added or subtracted from modes other than those in which the initial Gaussian state factorizes. Experimental data is leveraged to evaluate the potential for generating states with non-positive Wigner functions, further underscoring the feasibility of this approach in real-world scenarios.
The implications of these findings are profound for quantum information theory, suggesting pathways for creating quantum states with properties conducive to enhanced quantum information protocol performance. The research anticipates future developments where the synergy between theoretical insights and experimental practice in mode-selective photon operations will enable novel advances in quantum computation and communication.
The research posits questions about the extension of these findings to more complex quantum states, stimulating further exploration into the breadth of optical quantum operations. Anticipating the transition from laboratory to practical implementations, the paper paves the way for refined quantum technologies capable of surpassing existing paradigms.