Signal acquisition via polarization modulation in single photon sources

Abstract

A simple model system is introduced for demonstrating how a single photon source might be used to transduce classical analog information. The theoretical scheme results in measurements of analog source samples that are (i) quantized in the sense of analog-to-digital conversion and (ii) corrupted by random noise that is solely due to the quantum uncertainty in detecting the polarization state of each photon. This noise is unavoidable if more than one bit per sample is to be transmitted, and we show how it may be exploited in a manner inspired by suprathreshold stochastic resonance. The system is analyzed information theoretically, as it can be modeled as a noisy optical communication channel, although unlike classical Poisson channels, the detector's photon statistics are binomial. Previous results on binomial channels are adapted to demonstrate numerically that the classical information capacity, and thus the accuracy of the transduction, increases logarithmically with the square root of the number of photons, N . Although the capacity is shown to be reduced when an additional detector nonideality is present, the logarithmic increase with N remains.Extensive efforts to establish practical quantum computers incorporating quantum communication and/or cryptography have led towards the development of reliable Single Photon Sources (SPS) [1,2]. While much research in this area is targeted towards quantum information processing, and the concept of qubits [3], the impending availability of a reliable SPS may also have broader application.Here we introduce and analyze a paradigm of quantum photonic information processing that falls beyond the scope of classical Poisson light [4,5,6,7], sub-Poisson squeezed light [8] and the usual focus of quantum information theory [3]. We consider a model for the transduction of classical information via a quantum optical channel and a classical detector.In our model, an information source directly modulates a SPS that emits photons with equal energy at a known constant rate. Unlike the Poisson or sub-Poisson statistics of a classical optical source, this results in deterministic photon release counts. Significant recent experimental progress [2,9] indicates that an SPS may soon offer the possibility of modulation of the information source onto quantum properties of individual photons, namely the polarization angle. Thus the focus of this paper is on quantifying the potential benefits from exploiting such a controllable SPS polarization angle in sensing applications.We model the information source to be sensed (the 'signal') using the standard information theoretic approach, i.e. we treat the signal as a discrete random variable. While our system results in a quantum information channel, it is capable of transmitting classical information, as considered, e.g., in [10,11]. This is similar to the scenario in [10,12] where two photons are considered in the context of the Holevo bound [3]. However it differs in that we specify that an arbitrary (but constant) number of photons, N , are use...

Information capacity in the weak-signal approximation

“…The theory has been applied successfully to a wide range of problems [2], including, e.g., classical and quantum computation and communication [3][4][5], optical communication [6][7][8] or quantification of different aspects of information processing in real neurons and neuronal models [9][10][11][12][13][14][15].…”

“…Information theory is a mathematical framework that provides tools for quantification of information content and information transfer in systems defined by general probabilistic rules [1]. The theory has been applied successfully to a wide range of problems [2], including, e.g., classical and quantum computation and communication [3][4][5], optical communication [6][7][8] or quantification of different aspects of information processing in real neurons and neuronal models [9][10][11][12][13][14][15].…”