Physicists have demonstrated for the first time that the quantum vacuum—the sea of fluctuating electromagnetic fields that pervades empty space—can be engineered to strengthen superconductivity in a bulk material. The finding, from a collaboration between researchers at the University of Science and Technology of China (USTC) and the Massachusetts Institute of Technology (MIT), introduces a new concept the team calls «vacuumtronics».
The experiment showed that placing the layered superconductor niobium diselenide (NbSe₂) inside a specially designed near-terahertz split-ring resonator—a «dark cavity»—raised its superconducting critical temperature by up to 5.4% compared with regions of the same material outside the cavity. The researchers also observed substantial increases in the critical current and critical magnetic field near the transition temperature.
In quantum electrodynamics, a vacuum is not empty. It hosts fluctuating electromagnetic fields in which pairs of virtual particles are continuously created and annihilated. These vacuum fluctuations are already known to drive phenomena such as the Lamb shift, spontaneous emission, and the Casimir effect. In recent years, scientists have explored whether such fluctuations could be amplified to modify the properties of bulk matter, using resonant cavities to boost their strength by factors of 100 or more. Enhanced vacuum fields have previously been used to alter chemical reactivity, topological states, and conductivity.
The new work, led by Changgan Zeng and Guanghui Cheng at USTC, extends that approach to superconductivity. The team partially embedded a single NbSe₂ flake in the dark cavity and compared the material's resistance as a function of temperature inside and outside the resonator. Because both regions came from the same flake, the comparison controlled for sample-to-sample variation. The cavity is «dark» in the sense that no light shines on the material and no energy is actively pumped into it. As Cheng explains, the effect arises instead from the ever-present electromagnetic fluctuations of the quantum vacuum.
Distinguishing genuine vacuum-fluctuation effects from mundane explanations such as sample inhomogeneity, strain, or device fabrication artifacts was a central challenge. The researchers say they invested considerable effort in control experiments to rule these out. Their theorist colleagues, Qingdong Jiang of Shanghai Jiao Tong University and Frank Wilczek of MIT, developed a model within the Ginzburg–Landau framework. They hypothesize that the superconducting state exchanges virtual photons with the dark cavity, lowering its energy and thereby strengthening superconductivity. When the characteristic energy of the cavity mode matches the low-energy superconducting fluctuations, the device exhibits resonant enhancement, producing the peak in the effect.
Wilczek framed the result in broad terms. «In most practical physics experiments, the vacuum serves merely as the passive stage on which such phenomena play out,» he said. «Our work shows that the background itself can become an actor—engineered to strengthen superconductivity and reshape the behaviour of quantum matter.»
Zeng described the work as establishing quantum-vacuum engineering as a new non-invasive way to tune superconductivity. Although the temperature enhancement is modest, he said it is a proof of principle for what could become a broadly applicable approach. It could be relevant to superconducting circuits, quantum sensors, and other quantum devices, where non-invasive control of superconducting properties would be particularly valuable. More broadly, engineered vacuum fields could also be used to control states of matter beyond superconductivity.
The China–US team says it now aims to further enhance the effect through improved cavity and material design, and to continue investigating the underlying microscopic mechanisms in collaboration with theorists.