2017/11/30 by Peter Grünwald, P. Grünwald
Computer Science · Physics and Astronomy · #Algorithm #Correlation function (quantum field theory) #Field (mathematics) #Figure of merit #Fock space #Function (biology) #Optics #Order (exchange) #Photon #Physics #Projection (relational algebra) #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum mechanics #Quantum optics and atomic interactions #State (computer science) #cond-mat.mes-hall #quant-ph
paper · pdf · doi:10.1088/1367-2630/ab3ae0
published as New J. Phys. 21, 093003 (2019) · published version
openalex created_date 2019/05/29 · openalex publication_date 2019/08/13 · arxiv created 2019/09/12 · arxiv updated 2019/09/13 · openalex updated_date 2026/08/06
Abstract Quantum-optical research on semiconductor single-photon sources puts special emphasis on the measurement of the second-order correlation function g (2) ( τ ), arguing that g (2) (0) < 1/2 implies the source field represents a good single-photon light source. We analyze the gain of information from g (2) (0) with respect to single photons. Any quantum state, for which the second-order correlation function falls below 1/2, has a nonzero projection on the single-photon Fock state. The amplitude p of this projection is arbitrary, independent of g (2) (0). However, one can extract a lower bound on the single-to-multi-photon-projection ratio. A vacuum contribution in the quantum state of light artificially increases the value of g (2) (0), cloaking actual single-photon projection. Thus, we propose an effective second-order correlation function <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>2</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:msup> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> , which takes the influence of vacuum into account and also yields lower and upper bounds on p . We consider the single-photon purity as a standard figure of merit in experiments, reinterpret it within our results and provide an effective version of that physical quantity. Besides comparing different experimental and theoretical results, we also provide a possible measurement scheme for determining <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>2</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:msup> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> .