Processing Information by Punctuated Spin Superradiance

Abstract

The possibility of realizing the regime of punctuated spin superradiance is advanced. In this regime, the number of superradiant pulses and the temporal intervals between them can be regulated. This makes it feasible to compose a kind of the Morse Code alphabet and, hence, to develop a technique of processing information. 76.20.+q, 76.60.Es, 07.55.Yv, 85.90.+h Spin systems can exhibit a phenomenon that is analogous to atomic superradiance [1,2], because of which it is called spin superradiance. To realize this phenomenon, spin systems, similarly to atomic ones, are to be prepared in an inverted state. This is achieved by placing a polarized spin sample in an external magnetic field directed opposite to spin polarization. Contrary to atomic systems, coherent spin motion develops not owing to direct spin correlations but due to the interaction of spins with a resonator feedback field, for which purpose the spin sample has to be coupled with a resonant electric circuit, whose natural frequency is tuned to the Zeeman frequency of spins [3]. More details on similarities and differences between atomic superradiance and spin superradiance can be found in the review [4]. Spin superradiance is the process of coherent spontaneous emission by moving spins. As in the case of atomic systems, one may distinguish two main types of this phenomenon, transient superradiance and pulsing superradiance. Transient spin superradiance occurs when the spin sample is prepared in the inverted state, after which no following pumping is involved. In this case, a single superradiant burst arises, peaked at the delay time. Pulsing spin superradiance is radically different from the transient regime by the occurrence of a series of superradiant pulses, for which the spin sample is to be subject to a permanent pumping supporting the inverted spin polarization. Both regimes of spin superradiance, transient [5][6][7][8] as well as pulsing [9][10][11] were observed in experiments with different materials containing nuclear spins. A microscopic theory of these phenomena, based on realistic spin Hamiltonians, was developed [12][13][14][15], being in good agreement with experiment and with computer modelling [16]. It is worth stressing that only by invoking microscopic Hamiltonians it has become possible to give an accurate description of purely self-organized regimes which cannot be treated by the phenomenological Bloch equations [12][13][14].In the present paper, we advance the possibility of realizing the third type of spin superradiance, which we call punctuated spin superradiance, and which is principally different from the transient and pulsing types. In this regime, unlike the transient case, not a single but many superradiant bursts can be produced. In distinction to the pulsing regime, where the number of pulses and the temporal distance between them are prescribed by a given setup and cannot be varied, in the process of punctuated superradiance both the number of superradiant bursts as well as time intervals between each pair of them can ...

Atomic squeezing under collective emission

“…The regime of punctuated spin superradiance was suggested in Ref. 50. The situation for atomic systems is analogous to that for spin assemblies.…”

The Purcell-Dicke effect in the emission from a coated small sphere of resonant atoms placed inside a matrix cavity

“…This work expands on recent research on superra diance of atoms [6][7][8][9] in that it explores a solvable model, which represents a potentially realizable phys ical system where in addition to the cooperative effects resulting from the close proximity of identical atoms, I am also exploring the effects of the cavity on the sys tem's cooperative decay, a feature which so far has not been explored except in spin superradiance [10][11][12][13][14][15][16][17]. Yukalov and collaborators have shown that the pres ence of a resonator is crucial to spin superradiance.…”

Absence of spin superradiance in resonatorless magnets

“…The possibility of realizing spin superradiance by molecular magnets, coupled to a resonator, was advanced in Ref. [10], being based on the well developed theory [3][4][5][6][7][8][9][10][11]. At the same time, there have appeared speculations that spin superradiance in molecular magnets could be produced without coupling them to a resonant circuit, but in a way completely equivalent to atomic superradiance, so that the collectivization in spin motion would be due solely to their interactions through the common radiation field.…”

“…In order to realize spin superradiance, it is necessary to couple a polarized magnet to a resonant electric circuit. The collectivization of spin motion happens due to the resonator feedback field, which, thus, replaces the common radiation field [3][4][5][6][7][8][9][10][11]. The analogies and differences in atomic and spin superradiance have been extensively analysed in reviews [3,4,14].…”

“…[3,4]. An accurate microscopic theory of spin superradiance has recently been developed [5][6][7][8][9][10][11] demonstrating that, despite many similarities between the atomic and spin superradiance, these phenomena possess features that radically distinguish the spin from atomic superradiance [3][4][5][6][7][8][9][10][11]. The main such a fundamental difference is that the spin superradiance in real systems cannot be caused by their magnetodipole radiation field.…”