Quantum optics with electron waves

Sergey V. Gaponenko

Let us return from optics to mechanics and explore the analogy to its fullest extent. In optics the old system of mechanics corresponds to intellectually operating with isolated mutually independent light rays. The new undulatory mechanics corresponds to the wave theory of light . Erwin Schrödinger, Nobel lecture , 1933 In this chapter we shall see that electromagnetic waves and electrons feature a number of common properties under conditions of spatial confinement. Simple and familiar problems from introductory quantum mechanics and textbook wave optics are recalled in this chapter to emphasize the basic features of waves in spatially inhomogeneous media. Herewith we make a first step towards understanding the properties of electrons and electromagnetic waves in nanostructures and notice that these properties in many instances are counterparts. Different formulas and statements of this chapter can be found in handbooks on quantum mechanics and wave optics. A few textbooks on quantum mechanics do consider analogies of propagation and reflection phenomena in wave optics with those in wave mechanics. Isomorphism of the Schrödinger and Helmholtz equations In Chapter 2 we discussed that an electron in quantum mechanics is described by the wave function, the square of its absolute value giving the probability of finding an electron at a specific point in space. This function satisfies the Schrödinger equation (2.56) which is the second-order differential equation with respect to space and the first-order differential equation with respect to time.

Ruslan P. Ozerov, Anatoli A. Vorobyev

Charles Hard Townes

Quantum optics or electronics, discussing electromagnetic waves control and interactions with matter, maser oscillators theory and characteristics, nonlinear optics, induced transparency, etc

S. Chua

Svetlana Churochkina, Dmitry Churochkin

A recently developed relativistic quantum optics approach for a fast electron beam-optical modes interaction problem (Optica 6, 1524--1534 (2019)) contains suggestion about a smallness of the error induced by replacement $Ψ_{\vec k}\approxΨ_{\vec k_0}$ for noninteracting free electron Dirac spinors at such wave vector $\vec k$ that $\left|\vec k-\vec k_0 \right| \ll\left|\vec k_0\right|$ with $\vec k_0$ as a peaked wave vector of a focused electron beam. Here, based on quantum information approach we strictly investigated a degree of coincidence of spinors $Ψ_{\vec k}$ and $Ψ_{\vec k_0}$ by calculating fidelity for them. The analytical expression is obtained. It is shown that the fidelity inevitably depends on not only wave vectors $\vec k$ and $\vec k_0$ but also on mutual orientation of $[\vec k_0,\vec k]$ and $\hat{\vec{s}}^{\dagger}\vecσ\hat{\vec{s}}$ with $\vec{s}$ is a two-component spin unit vector and $\vecσ$ is a vector of Pauli matrices. This result can be conceived as a chirality-like effect in the fidelity and constraints spin arbitrariness when applying the developed relativistic quantum optics approach to the problems of interest. A geometrical configuration of $\vec k_0$, $\vec k-\vec k_0$, and $\hat{\vec{s}}^†\vecσ\hat{\vec{s}}$ that is optimal in terms of fidelity is established.

Benjamin Roussel, Clément Cabart, Pascal Degiovanni