Quantifying quantum coherence of optical cat states

Abstract

Optical cat state plays an essential role in quantum computation and quantum metrology. Here, we experimentally quantify quantum coherence of an optical cat state by means of relative entropy and l 1 norm of coherence in Fock basis based on the prepared optical cat state at rubidium D1 line. By transmitting the optical cat state through a lossy channel, we also demonstrate the robustness of quantum coherence of optical cat state in the presence of loss, which is different from the decoherence properties of fidelity and Wigner function negativity of the optical cat state. Our results confirm that quantum coherence of optical cat states is robust against loss and pave the way for the application with optical cat states.

Experimental Progress on Quantum Coherence: Detection, Quantification, and Manipulation

“…Besides quantum coherence concerning discrete variables, coherence of continuous variables has also been experimentally studied recently. [ 120,121 ]…”

Theory of Photon Subtraction for Two-Mode Entangled Light Beams

“…Equation ( 8) comprises information that is necessary to describe the photon subtraction (7) of an input state |ψ(α) . The related output |Ψ B is a linear superposition of entangled bipartite states whose probability amplitudes yield the probability (14). Each element in the superposition links a photon number state |n a of mode a with the n-subtracted state (9) of |ψ(α) in mode b. Additionally, Equations ( 15) and ( 16) provide the above formulae assuming that the input state |ψ(α) is composited only of either even-number states or odd-number states, respectively.…”

“…This issue is of great interest because the Glauber states, formed by superpositions of photon-number states, tolerate a description in terms of the Maxwell theory [5], so they may describe the states of macroscopic systems. The creation of cat states, a theoretical description introduced by Schrödinger to show the way in which quantum mechanics contradicts our everyday experience for systems as great as a 'cat' [11], therefore, is available in the laboratory using even and odd coherent states [12,13], which are, therefore, called optical cat states [14] (although the term optical kitten is also found [15]).…”

Theory of Photon Subtraction for Two-Mode Entangled Light Beams

“…Equation ( 8) comprises information that is necessary to describe the photon subtraction (7) of an input state |ψ(α) . The related output |Ψ B is a linear superposition of entangled bipartite states whose probability amplitudes yield the probability (14). Each element in the superposition links a photon number state |n a of mode a with the n-subtracted state (9) of |ψ(α) in mode b. Additionally, Eqs.…”

“…This issue is of great interest because the Glauber states, formed by superpositions of photon-number states, tolerate a description in terms of the Maxwell theory [5], so they may describe the states of macroscopic systems. The creation of cat states, a theoretical description introduced by Schrödinger to show the way in which quantum mechanics contradicts our everyday experience for systems as great as a 'cat' [11], is therefore available in the laboratory using even and odd coherent states [12,13], which are therefore called optical cat states [14] (although the term optical kitten is also found [15]).…”