Writing Electronic Ferromagnetic States in a High-Temperature Paramagnetic Nuclear Spin System

Abstract

In this paper we use the Nuclear Magnetic Resonance (NMR) to write eletronic states of a ferromagnetic system into a high-temperature paramagnetic nuclear spins. Through the control of phase and duration of radiofrequency pulses we set the NMR density matrix populations, and apply the technique of quantum state tomography to experimentally obtain the matrix elements of the system, from which we calculate the temperature dependence of magnetization for different magnetic fields. The effects of the variation of temperature and magnetic field over the populations can be mapped in the angles of spins rotations, carried out by the RF pulses. The experimental results are compared to the Brillouin functions of ferromagnetic ordered systems in the mean field approximation for two cases: the mean field is given by (i) B = B0 + λM and (ii) B = B0 + λM + λ ′ M 3 , where B0 is the external magnetic field, and λ, λ ′ are mean field parameters. The first case exhibits second order transition, whereas the second case has first order transition with temperature hysteresis. The NMR simulations are in good agreement with the magnetic predictions.

Carboxylate-based molecular magnet: One path toward achieving stable quantum correlations at room temperature

“…In spite of that, it is fragile and can easily vanish due to the inevitable interaction of the system with its environment [4]; and due to this condition, it was thought that entanglement could only exist at low temperatures. However, recently, it has been shown that entanglement can also exist at higher temperatures, and can be detected through the measurement of some thermodynamic observables [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…In spite of that, it is fragile and can easily vanish due to the inevitable interaction of the system with its environment [4]; and due to this condition, it was thought that entanglement could only exist at low temperatures. However, recently, it has been shown that entanglement can also exist at higher temperatures, and can be detected through the measurement of some thermodynamic observables [5][6][7][8][9][10][11][12][13][14][15][16][17].Nevertheless, quantum entanglement does not encompass all quantum correlations in a system and recent studies have greatly expanded the notion of quantum correlations [18][19][20][21][22][23][24][25][26][27][28][29]; and the measure of quantum excess of correlations has been named as quantum discord [19][20][21]. In the last years, it was understood that quantum discord has an important role in many quantum information processing even without entanglement.…”

Quantifying quantum coherence in a metal-silicate framework

“…In recent years, it has been demonstrated that molecular magnetic systems present themselves as strong candidates as prototype materials for emerging quantum devices, and the characterization of its quantum correlations has received a considerable attention [2,[4][5][6][7][8][12][13][14][15]. Recently, it has been demonstrated that this systems may be immune to decoherence mechanisms, presenting highly stable quantum correlations against external perturbations such as temperature and magnetic fields [2,[4][5][6][7][8][12][13][14][15].…”

“…In recent years, it has been demonstrated that molecular magnetic systems present themselves as strong candidates as prototype materials for emerging quantum devices, and the characterization of its quantum correlations has received a considerable attention [2,[4][5][6][7][8][12][13][14][15]. Recently, it has been demonstrated that this systems may be immune to decoherence mechanisms, presenting highly stable quantum correlations against external perturbations such as temperature and magnetic fields [2,[4][5][6][7][8][12][13][14][15]. On the other hand, while the entanglement and nonclassical correlations (or quantum correlations) are a key resource to characterize the quantum properties of a bipartite and some multipartite systems, quantum coherence is a common necessary condition for different forms of quantum correlations [16,17], being a fundamental feature for signifying quantumness in an integral system [17].…”

Quantum information processing by nuclear magnetic resonance on quadrupolar nuclei

“…As a way to overcome these limitations, we proposed a QST method using only short non-selective RF pulses with a coherence selection scheme [10]. As a result, many studies involving quadrupolar nuclei could benefit from that method, including research on quadrupolar spin decoherence and relaxation [11][12][13][14] and quantum simulation [15]. Section 2 briefly expounds the main concepts regarding PPS and logic gate implementation and QST in high-field NMR of quadrupolar nuclei.…”