A new photosensitive neuron model and its dynamics

Biological neurons can receive inputs and capture a variety of external stimuli,which can be encoded and transmitted as different electric signals.Thus,the membrane potential is adjusted to activate the appropriate firing modes.Indeed,reliable neuron models should take intrinsic biophysical effects and functional encoding into consideration.One fascinating and important question is the physical mechanism for the transcription of external signals.External signals can be transmitted as a transmembrane current or a signal voltage for generating action potentials.We present a photosensitive neuron model to estimate the nonlinear encoding and responses of neurons driven by external optical signals.In the model,a photocell(phototube)is used to activate a simple FitzHugh-Nagumo(FHN)neuron,and then external optical signals(illumination)are imposed to excite the photocell for generating a time-varying current/voltage source.The photocell-coupled FHN neuron can therefore capture and encode external optical signals,similar to artificial eyes.We also present detailed bifurcation analysis for estimating the mode transition and firing pattern selection of neuronal electrical activities.The sampled time series can reproduce the main characteristics of biological neurons(quiescent,spiking,bursting,and even chaotic behaviors)by activating the photocell in the neural circuit.These results could be helpful in giving possible guidance for studying neurodynamics and applying neural circuits to detect optical signals.

High-capacity quantum secure direct communication with two-photon six-qubit hyperentangled states

This study proposes the first high-capacity quantum secure direct communication(QSDC) with two-photon six-qubit hyperentangled Bell states in two longitudinal momentum and polarization degrees of freedom(DOFs) of photon pairs, which can be generated using two 0.5 mm-thick type-I β barium borate crystal slabs aligned one behind the other and an eight-hole screen. The secret message can be independently encoded on the photon pairs with 64 unitary operations in all three DOFs. This protocol has a higher capacity than previous QSDC protocols because each photon pair can carry 6 bits of information, not just 2 or 4 bits.Our QSDC protocol decreases the influence of decoherence from environment noise by exploiting the decoy photons to check the security of the transmission of the first photon sequence. Compared with two-way QSDC protocols, our QSDC protocol is immune to an attack by an eavesdropper using Trojan horse attack strategies because it is a one-way quantum communication.The QSDC protocol has good applications in the future quantum communication because of all these features.

Self-error-rejecting photonic qubit transmission in polarization-spatial modes with linear optical elements

We present an original self-error-rejecting photonic qubit transmission scheme for both the polarization and spatial states of photon systems transmitted over collective noise channels. In our scheme, we use simple linear-optical elements, including half-wave plates, 50:50 beam splitters, and polarization beam splitters, to convert spatial-polarization modes into different time bins. By using postselection in different time bins, the success probability of obtaining the uncorrupted states approaches 1/4 for singlephoton transmission, which is not influenced by the coefficients of noisy channels. Our self-error-rejecting transmission scheme can be generalized to hyperentangled n-photon systems and is useful in practical high-capacity quantum communications with photon systems in two degrees of freedom.