Quantum energy teleportation (QET), implemented via local operations and classical communication, enables carrier-free energy transfer by exploiting quantum resources. While QET has been extensively studied theoretically and validated experimentally in various quantum platforms, enhancing energy output for mixed initial states, as the system inevitably interacts with environments, remains a significant challenge. In this work, we study QET performance in a two-qubit system coupled to equilibrium or nonequilibrium reservoirs. We derive an analytical expression for the energy output in terms of the system Hamiltonian eigenstates, enabling analysis of energy output for mixed states. Using the Redfield master equation, we systematically examine the effects of qubit detuning, nonequilibrium temperature difference, and nonequilibrium chemical potential difference on the energy output. We find that the energy output for mixed states often follows that of the eigenstate with the highest population, and that nonequilibrium environments can enhance the energy output in certain parameter regimes.
Quantum energy teleportation (QET), implemented via local operations and classical communication, enables carrier-free energy transfer by exploiting quantum resources. While QET has been extensively studied theoretically and validated experimentally in various quantum platforms, enhancing energy output for mixed initial states, as the system inevitably interacts with environments, remains a significant challenge. In this work, we study QET performance in a two-qubit system coupled to equilibrium or nonequilibrium reservoirs. We derive an analytical expression for the energy output in terms of the system Hamiltonian eigenstates, enabling analysis of energy output for mixed states. Using the Redfield master equation, we systematically examine the effects of qubit detuning, nonequilibrium temperature difference, and nonequilibrium chemical potential difference on the energy output. We find that the energy output for mixed states often follows that of the eigenstate with the highest population, and that nonequilibrium environments can enhance the energy output in certain parameter regimes.
Quantum teleportation, a fundamental protocol in quantum information science, enables the transfer of quantum states through entangled particle pairs and classical communication channels. While ideal quantum teleportation requires maximally entangled states as resources, real-world implementations inevitably face environmental noise and decoherence effects. In this work, we investigate quantum teleportation in nonequilibrium environments with different temperatures or chemical potentials. We employ the Bloch-Redfield equation to characterize the nonequilibrium dynamics in both bosonic and fermionic reservoirs. Our analysis reveals that nonequilibrium conditions, namely, the temperature difference and chemical potential difference, can significantly enhance the teleportation fidelity beyond what is achievable in equilibrium scenarios. Notably, under certain nonequilibrium conditions, the fidelities for all input states converge to the same value. We term this behavior the teleportation with a fixed-point fidelity. Importantly, at this fixed point, fidelity can be further enhanced by tuning the nonequilibrium parameters. These findings offer crucial insights for the implementation of quantum communication protocols in realistic environments, demonstrating that nonequilibrium conditions not only improve the fidelity but also present a promising avenue for simplifying practical quantum teleportation schemes.
In this work, we explore quantum energy teleportation (QET) protocols, focusing on their behavior at finite temperatures , in ground and excited states. We analyze the role of entanglement as a resource for QET, particularly in thermal states, and compare the performance of QET across these initial states. We then introduce a method to extract ground-state energy through a protocol that employs only quantum measurements, local operations, and classical communication (LOCC), without requiring the ground state to be quantum correlated either through entanglement or quantum discord. To illustrate this, we propose a minimal model comprising two interacting qubits. These findings indicate that, in addition to the established QET framework where quantum correlation serves as a resource, it is possible to extract energy from an product ground state. This broadens the scope of QET's applicability across diverse quantum systems.
Quantum Energy Teleportation (QET) exploits quantum entanglement and local operations with classical communication (LOCC) to transfer energy between distant locations without physically transporting the energy carrier. Previous demonstrations on superconducting hardware employed a two-qubit architecture and achieved a work extraction efficiency of approximately 11.7%. In this work, we propose a three-qubit QET protocol based on a novel Ising-model Hamiltonian satisfying the zero-mean-energy condition and the commutation and anti-commutation constraints required for QET. We investigate two complementary protocols. In the Single-Input Multiple-Output (SIMO) configuration, a single sender injects energy while two receivers jointly extract negative energy. Retaining all interaction terms, including the inter-receiver coupling, yields an honest work extraction efficiency of approximately 8--10%, comparable to the two-qubit implementation while distributing the extracted energy across two receivers. In the Multiple-Input Single-Output (MISO) configuration, two senders jointly inject energy through a single entangle-then-measure operation, and one receiver extracts the teleported energy. After subtracting the energy deposited directly into the receiver by the entangling operation, the net teleportation efficiency reaches 34--42%, substantially exceeding the two-qubit protocol while remaining consistent with energy conservation. These results show that extending QET to a three-qubit many-body system can significantly improve teleportation efficiency and provide a framework for studying energy transport, negative-energy distributions, and more complex quantum many-body dynamics.
Quantum energy teleportation (QET) is a protocol that enables the extraction of positive energy from a local subsystem by exploiting ground-state entanglement and classical communication, without any physical carrier transporting energy between distant parties. In this work, we propose and analyze a QET protocol implemented in strongly driven atomic systems subjected to intense classical fields. We model a pair of interacting two-level atoms (or effective few-level systems) driven by a strong, time-dependent field and coupled via dipole–dipole or mediated interactions. The strong field creates a nontrivial, Floquet-engineered energy landscape and modifies the structure of ground-state and steady-state correlations. Within this setting, we construct local energy density operators and identify regimes in which negative local energy densities are dynamically generated and can be accessed via local measurements. We then formulate a QET protocol in which Alice performs a local measurement on her strongly driven atom, injects energy into the system, and sends the classical outcome to Bob, who performs a conditional local unitary on his distant atom to extract positive energy from the strongly driven environment. We derive explicit expressions for the teleported energy and analyze its dependence on driving strength, detuning, atom–atom coupling, and measurement parameters. Our results demonstrate that strong-field driving can enhance the amount of teleported power , extend the QET operating range to non-equilibrium Floquet regimes, and provide a feasible route toward realizing QET in tabletop atomic platforms driven by intense laser fields.
This study investigates quantum energy teleportation (QET) using stochastic bi-partitioning in an N−body Hamiltonian system. In this protocol, project measurements are performed on (N−m) qubits to capture quantum fluctuation information of the N−qubit ground state during external energy injection. Significantly, the information reaches the sites of the remaining m qubits faster than the energy diffuses, allowing for extracting the ground state energy through local operations. Our results show that increasing the number of qubits N enhances the available energy for QET, with efficiency peaking when (N−1) qubits are inputs and one is an output. We also find a strong correlation between energy transfer efficiency and ground-state entanglement. Increasing the parameter hk improves both efficiency and entanglement until reaching a plateau. Overall, more qubits lead to higher energy transfer efficiency and entanglement, highlighting their critical roles in QET performance.
Quantum energy teleportation (QET) has been proposed to overcome the restrictions of strong local passivity (SLP) and to facilitate energy transfer in quantum systems. Traditionally, QET has only been considered under strict constraints, including the requirements that the initial state be the ground state of an interacting Hamiltonian, that Alice's measurement commute with the interaction terms, and that entanglement be present. These constraints have significantly limited the broader applicability of QET protocols. In this work, we demonstrate that SLP can arise beyond these conventional constraints, establishing the necessity of QET in a wider range of scenarios for local energy extraction. This leads to a more flexible and generalized framework for QET. Furthermore, we introduce the concept of a "local effective Hamiltonian," which eliminates the need for optimization techniques in determining Bob's optimal energy extraction in QET protocols. As an additional advantage, the amount of energy that can be extracted using our new protocol is amplified to be 7.2 times higher than that of the original protocol. These advancements enhance our understanding of QET and extend its broader applications to quantum technologies. To support our findings, we implement the protocol on quantum hardware, confirming its theoretical validity and experimental feasibility.