Quantum Energy Teleportation: From Two Qubits to Networks of Five ✦
Quantum energy teleportation (QET) has, for the first time, been realized on a platform exceeding two qubits. A multi-party QET protocol capitalizing on robust multipartite entanglement in the W-state was designed and experimentally validated. Three-, four-, and five-qubit schemes were executed on both error-free simulators and IBM superconducting hardware. In every scenario, one sender supplies energy E0, which is then deterministically extracted in a step-down manner by multiple remote receivers. This confirms that energy deposited at a single node can be redistributed among numerous entangled subsystems with classical delay bounded by the speed of light. The results pave a practical route toward energy‑aware quantum networks.
Context
As early as Erwin Schrödinger dubbed quantum entanglement the most striking feature of the micro-world. Today we know that entanglement is not just a philosophical curiosity, but a valuable resource. Quantum energy teleportation (QET) protocols, proposed in 2008, allow energy to be extracted from the ground state of an entangled system via local measurements and classical communication. Until now, all experiments were limited to two particles, but building distributed quantum networks requires scaling to multi-particle systems. The problem is that in the common GHZ state, measuring one qubit destroys the entanglement of all others. The real breakthrough became possible thanks to W-states, whose loss-resilience was predicted theoretically and has now been embodied in silicon.
Methods
The researchers devised an optimized scheme for multipartite entanglement of the W type on chains of three, four, and five superconducting qubits. Unlike the traditional approach, the number of gates was reduced from linear to logarithmic, which is critical on noisy NISQ processors. After superposition initialization, one qubit—'Alice'—underwent a projective measurement, injecting energy E₀. The classical bit with the measurement outcome was sent to the other participants—'Bob', 'Charlie', and so on—who applied a feed-forward unitary operation to correct the phase and then performed local energy measurements. The whole process adheres to LOCC (local operations and classical communication) principles, so the energy transfer speed is bounded by the speed of light, consistent with causality. Experiments were run on a simulator and the real IBM Lagos device, with noise maps characterized.
Results
In all configurations, the injected energy E₀ was distributed among remote receivers in a strictly decremental order: the first measured receiver extracted the largest share, and each subsequent one less and less. For example, for three qubits on the simulator with E₀=0.707 a.u., the first receiver got 0.526, the second 0.170 (sum 0.696), which is 98% of the input energy. On the real processor, due to decoherence and noise, the figures fluctuated slightly, but the qualitative picture held: energy was never 'lost' without a trace; it was redistributed within the entangled ensemble. Additional tests confirmed translational symmetry (the subsystem Hamiltonian is the same when measured from any node) and exchange symmetry (the order of querying the receivers does not change the final values). These checks rule out parasitic effects and prove that the observed distribution is an intrinsic property of the W-protocol.
Implications
The results demonstrate for the first time that quantum information can not only transmit data but also serve as an energy carrier in multi-node networks. This changes the perspective on the thermodynamics of entangled systems: energy does not simply dissipate; it is controllably redistributed via a classical signal. The link between entanglement and available work, previously discussed in the context of Bell's inequalities and the EPR paradox, gains a rigorous operational foundation. It becomes possible to create 'energy quantum networks' where each node can donate or receive energy without physical contact, subject only to light-speed delay.
Future development
The W-state platform is easily scalable, and the next logical step is implementation on dozens of qubits using quantum repeaters. Alternative resource states, such as cluster or hyperentangled ones, could boost transfer efficiency. Hybrid photon-superconducting architectures promise to take the protocol to kilometer-scale distances. An even more intriguing prospect is using QET for topological order spectroscopy: by varying the energy injection method, one could probe exotic phases of matter, identifying them by their response to energy perturbations.
Impact
The development directly impacts the architecture of future quantum internet networks and data centers, where heat management is becoming critical.
Next steps
The immediate task is integration with error correction methods and transfer to platforms with longer coherence times, as well as experimental verification on fiber-optic communication lines.
Key open problems
The protocol sharpens a fundamental question: exactly how does quantum state reduction upon measurement redistribute energy in a composite system? It also touches on the 'Maxwell's demon' paradox in the quantum realm—gaining energy through knowledge of the system without apparent heat exchange—and calls for rethinking the second law of thermodynamics for strongly entangled many-body ensembles.
🎯 Although the protocol is called teleportation, energy does not vanish in one place and appear in another; it is extracted from the shared ground state, much like a loan taken from a bank's general fund while preserving the overall balance.
Key numbers
- injected energy (h=k=1, 3 qubits): 0.7071 a.u.
- energy of first receiver (simulator): 0.5255 a.u. (74%)
- energy of second receiver (simulator): 0.1702 a.u. (24%)
- total extracted energy (simulator): about 98% of E₀
- deviation on real device (ibm_lagos): sum ~0.72 a.u. due to noise