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

Cruz, C., Diogo O. Soares-Pinto, Paula Brandão, A. M. dos Santos, Mario S. Reis

Published Jan 1, 2016• 4 citations
OpenAlex

Abstract

The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction. Copyright (C) EPLA, 2016

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

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The control of quantum correlations in solid state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this Letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.

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In the present work we show that a particular family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic-susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the copper carboxylate ${{\text{Cu}}_{2}{({\text{O}}_{2}\text{CH})}_{4}}{\text{Cu}{({\text{O}}_{2}\text{CH})}_{2}{(2\text{-methylpyridine})}_{2}}$, and we have found this to be above room temperature $({T}_{e}\ensuremath{\sim}630\text{ }\text{K})$. Furthermore, the results show that the system remains maximally entangled until close to $\ensuremath{\sim}100\text{ }\text{K}$ and the Bell's inequality is violated up to nearly room temperature $(\ensuremath{\sim}290\text{ }\text{K})$.

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We review the progress made in integrating magnetic molecules containing transition metal ions into nanoelectronic solid-state devices and using them as molecular spin qubits. Molecular spin qubits offer numerous advantages over other material platforms, such as being inherently quantum systems with discrete energy levels, having a rich variety of possible chemical designs, and being synthesizable in large quantities with atomic precision. However, the integration of magnetic molecules into practical and scalable molecular spin qubit devices (MSQDs) that offer initialization, coherent control, and readout of quantum spin states remains one of the major bottlenecks on the way toward applications of these systems in quantum computing technologies. We discuss the evolution of the field of MSQDs and review the first successful implementation of essential qubit operations in a single-molecule transistor based on a TbPc 2 molecule. Further development has been achieved through the merging of molecular electronics with the circuit quantum electrodynamics (cQED) approach where molecular spin states can be manipulated by the microwave frequency photons confined in a superconducting waveguide resonator. We discuss examples of such hybrid devices operating via coupling of a superconducting resonator to large spin ensembles, such as bulk samples and thin films. We also review a possible architecture for single-molecule cQED devices and the potential advantages that it offers. Then, we highlight the possibility and benefits of the optical initialization and readout of molecular spin states. This approach has been realized by using an optical pumping technique for the initialization and changes in photoluminescence for the readout of large molecular spin ensembles coupled to a superconducting resonator. The field of MSQDs is highly interdisciplinary, bringing together progress in synthetic chemistry, molecular electronics, cQED, and optical measurements. While it is still in its infancy, there are promising theoretical designs and encouraging proof-of-concept experiments, and we discuss several proposed device architectures that are eagerly awaiting experimental realization. Advances in hybrid MSQDs will open horizons for quantum technologies.

ACS Applied Electronic Materials•Jul 13, 2023•34 citations
The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction. Copyright (C) EPLA, 2016
The control of quantum correlations in solid state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this Letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.
Abstract The study of advanced quantum devices for energy storage has attracted the attention of the scientific community in the past few years. Although several theoretical progresses have been achieved recently, experimental proposals of platforms operating as quantum batteries under ambient conditions are still lacking. In this context, this work presents a feasible realization of a quantum battery in a carboxylate-based metal complex, which can store a finite amount of extractable work under the form of quantum discord at room temperature, and recharge by thermalization with a reservoir. Moreover, the stored work can be evaluated through non-destructive measurements of the compound’s magnetic susceptibility. These results pave the way for the development of enhanced energy storage platforms through material engineering.
General requirements for the materials for systems and devices whose operation is based on quantum correlations are discussed. The fluctuation theory of quantum entanglement is outlined. This theory allows one to estimate the size of the region of weak fluctuations of quantum entanglement for spin dimers in various materials. The concept of quantum discord as a measure of pure quantum correlations is outlined. Quantum correlations in polycrystalline samples of binuclear nitrosyl iron complexes were estimated from the temperature dependences of the magnetic susceptibilities. Particular attention is paid to calculations of the temperature corresponding to the emergence of quantum entanglement. Methods for increasing this temperature are discussed. The problem of the quantum information transmission as well as the future development of quantum technology is considered. The bibliography includes 120 references.
Abstract {The urgent demand for sustainable energy storage devices necessitates the development of novel conceptual and technological paradigms that extend beyond the constraints imposed by classical thermodynamic limits. in order to present the material innovations required to enable viable room-temperature quantum technologies, this Review outlines the potential of dinuclear Cu(II) complexes as promising model platforms for the development of room-temperature quantum batteries.} We address how the quantum properties of these dinuclear materials can be harnessed to store and extract energy, and how they can be handled and engineered by the management of the intra-molecular magnetic coupling and external thermodynamic conditions. {Through macroscopic magnetometric mappings, we present how the maximum extractable work (ergotropy) can be directly quantified without invasive quantum tomography. Furthermore, we review the operational simulation of these materials using quantum computing approaches using the Variational Quantum Thermalizer (VQT) algorithm on Noisy Intermediate-Scale Quantum (NISQ) devices. Finally, we provide an outlook on future research directions, highlighting the critical material engineering and quantum error mitigation strategies required to transition these coordination compounds from theoretical models to functional macroscopic solid-state quantum energy storage devices at room temperature.}
In the present work we show that a particular family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic-susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the copper carboxylate Cu2(O2CH)4Cu(O2CH)2(2-methylpyridine)2{{\text{Cu}}_{2}{({\text{O}}_{2}\text{CH})}_{4}}{\text{Cu}{({\text{O}}_{2}\text{CH})}_{2}{(2\text{-methylpyridine})}_{2}}Cu2​(O2​CH)4​Cu(O2​CH)2​(2-methylpyridine)2​, and we have found this to be above room temperature $({T}_{e}\ensuremath{\sim}630\text{ }\text{K})$. Furthermore, the results show that the system remains maximally entangled until close to $\ensuremath{\sim}100\text{ }\text{K}$ and the Bell's inequality is violated up to nearly room temperature $(\ensuremath{\sim}290\text{ }\text{K})$.
We review the progress made in integrating magnetic molecules containing transition metal ions into nanoelectronic solid-state devices and using them as molecular spin qubits. Molecular spin qubits offer numerous advantages over other material platforms, such as being inherently quantum systems with discrete energy levels, having a rich variety of possible chemical designs, and being synthesizable in large quantities with atomic precision. However, the integration of magnetic molecules into practical and scalable molecular spin qubit devices (MSQDs) that offer initialization, coherent control, and readout of quantum spin states remains one of the major bottlenecks on the way toward applications of these systems in quantum computing technologies. We discuss the evolution of the field of MSQDs and review the first successful implementation of essential qubit operations in a single-molecule transistor based on a TbPc 2 molecule. Further development has been achieved through the merging of molecular electronics with the circuit quantum electrodynamics (cQED) approach where molecular spin states can be manipulated by the microwave frequency photons confined in a superconducting waveguide resonator. We discuss examples of such hybrid devices operating via coupling of a superconducting resonator to large spin ensembles, such as bulk samples and thin films. We also review a possible architecture for single-molecule cQED devices and the potential advantages that it offers. Then, we highlight the possibility and benefits of the optical initialization and readout of molecular spin states. This approach has been realized by using an optical pumping technique for the initialization and changes in photoluminescence for the readout of large molecular spin ensembles coupled to a superconducting resonator. The field of MSQDs is highly interdisciplinary, bringing together progress in synthetic chemistry, molecular electronics, cQED, and optical measurements. While it is still in its infancy, there are promising theoretical designs and encouraging proof-of-concept experiments, and we discuss several proposed device architectures that are eagerly awaiting experimental realization. Advances in hybrid MSQDs will open horizons for quantum technologies.