An Energetic Constraint for Qubit-Qubit Entanglement

Quantum Physics [Submitted on 17 Mar 2026] An Energetic Constraint for Qubit-Qubit Entanglement Kiarn T. Laverick, Samyak P. Prasad, Pascale Senellart, Maria Maffei, Alexia Auffèves We analyze qubit-qubit entanglement from an energetic perspective and reveal an energetic trade-off between quantum coherence and entanglement. We decompose each qubit internal energy into a coherent and an incoherent component. The qubits' coherent energies are maximal if the qubit-qubit state is pure and separable. They decrease as qubit-qubit entanglement builds up under locally-energy-preserving processes. This yields a "coherent energy deficit" that we show is equal to a well-known measure of entanglement, the square negativity. In general, a qubit-qubit state can always be represented as a mixture of pure states. Then, the coherent energy deficit splits into a quantum component, corresponding to the average square negativity of the pure states, and a classical one reflecting the mixedness of the joint state. Minimizing the quantum deficit over the possible pure state decompositions yields the square negativity of the mixture. Our findings bring out new figures of merit to optimize and secure entanglement generation and distribution under energetic constraints. Comments: 5 Page Main + 3 Supplemental, 3 Figures. Comments Welcome! Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.16225 [quant-ph]   (or arXiv:2603.16225v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.16225 Focus to learn more Submission history From: Kiarn Laverick [view email] [v1] Tue, 17 Mar 2026 08:05:45 UTC (419 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)