Physicists have identified a new superfluid phase in a class of quantum systems that, until recently, looked too unstable and lossy to host such delicate order. Instead of destroying quantum coherence, the odd rules that govern these systems appear to carve out an entirely new regime of frictionless flow. The result is a fresh chapter in the story of superfluidity, one that connects exotic theory to fast‑moving experiments on ultracold atoms and engineered materials.
At the same time, laboratories are racing to pin down other unconventional superfluids, from counterflowing atomic clouds to atomically thin conductors that blur the line between metal and quantum fluid. Together, these advances suggest that superfluidity is not a rare curiosity but a flexible organizing principle for quantum matter, with implications for sensing, simulation and, eventually, quantum technologies that operate far from equilibrium.
What makes this new superfluid phase so unusual
The newly reported phase lives in what theorists call a non‑Hermitian quantum system, where particles can leak out, be pumped in or experience effective gain and loss that break the neat energy bookkeeping of textbook quantum mechanics. In such a setting, one would expect fragile collective states like superfluidity to collapse quickly, yet the researchers instead found a robust phase in which particles still move without resistance and maintain long‑range coherence. The key twist is that the rules of the game are modified: the spectrum of excitations and the way the fluid responds to disturbances are reshaped by the non‑Hermitian dynamics, so the phase is not just a copy of familiar superfluids transplanted into a messy environment.
According to the team behind the discovery, the stability of this phase is not an accident but a direct consequence of the underlying lattice geometry that hosts the particles. They report that the geometry dictates both how the superfluid forms and how it survives in different dimensions, turning the lattice into a kind of design knob for nonequilibrium quantum order. In their analysis, this makes the phase a prototype for what they describe as nonequilibrium strongly correlated quantum matter, where interactions, drive and dissipation all play essential roles rather than being treated as small corrections.
Non‑Hermitian quantum mechanics moves from curiosity to playground
For decades, non‑Hermitian Hamiltonians were mostly a mathematical curiosity, used to model open systems but rarely treated as a fertile ground for new phases of matter. The emergence of a superfluid in this context signals that non‑Hermitian physics is becoming a practical playground for engineering quantum behavior that cannot exist in closed, energy‑conserving systems. Instead of fighting loss and decoherence at all costs, researchers are starting to shape them, using carefully tuned gain and dissipation to sculpt effective interactions and stabilize exotic states.
This shift mirrors a broader trend in quantum science, where experimentalists routinely work with driven, lossy platforms such as photonic lattices, cold atoms in optical traps and solid‑state devices coupled to measurement circuits. In that landscape, a non‑Hermitian superfluid is not just a theoretical trophy, it is a template for how to harness open‑system effects to achieve controlled transport and coherence. By tying the phase to specific lattice geometries and dimensionalities, the study points toward concrete design rules that could be implemented in optical resonator arrays, patterned semiconductors or hybrid atom‑photon structures that naturally realize non‑Hermitian dynamics.
How lattice geometry and dimensionality steer the phase
One of the most striking claims in the new work is that the geometry of the lattice, not just the strength of interactions, sets the boundaries of the superfluid regime. In conventional Hermitian systems, changing from a one‑dimensional chain to a two‑ or three‑dimensional lattice already has a dramatic impact on how particles condense and flow. Here, the researchers argue that non‑Hermitian effects amplify that sensitivity, so that subtle changes in connectivity, coordination number or boundary conditions can flip the system from a stable superfluid to a fragile or even non‑superfluid state.
Dimensionality enters as a second control parameter, shaping how fluctuations and dissipation compete. In lower dimensions, quantum and thermal fluctuations usually destabilize long‑range order, but the analysis suggests that carefully arranged gain and loss can counteract that tendency and carve out pockets of stability. In higher dimensions, the same mechanisms can instead introduce new decay channels that erode coherence unless the lattice is tuned to suppress them. This interplay between geometry, dimension and non‑Hermitian dynamics turns the phase diagram into a multi‑dimensional map, where superfluidity occupies regions that would be inaccessible in more conventional settings.
Counterflow superfluidity shows the experimental frontier
The theoretical discovery of a non‑Hermitian superfluid lands in a year when experimentalists have already pushed the boundaries of what superfluidity can look like. In China, a team working with ultracold atomic gases reported a state known as counterflow superfluidity, in which two interpenetrating components move in opposite directions without friction. For the last two decades, physicists had treated this state as a kind of holy grail for multicomponent quantum fluids, because it requires precise control over interactions and relative motion that is difficult to achieve in the lab.
In their setup, the Chinese group used atomic ultracold gases to realize a regime where the two components could slide past each other while maintaining coherence, a feat that confirms long‑standing theoretical predictions about counterflowing quantum matter. The demonstration was described as a Quantum breakthrough and a world‑first observation of this particular flow pattern, underscoring how far experimental control over superfluids has come since the early days of liquid helium and simple Bose–Einstein condensates.
Chinese scholars and the rise of engineered quantum states
The counterflow result did not emerge in isolation. It is part of a broader push by Chinese institutions to engineer novel quantum states of matter in ultracold atomic systems, where parameters can be tuned with a precision that is impossible in traditional materials. Chinese scholars reported that they had observed this novel quantum state of matter, explicitly identifying it as counterflow superfluidity in atomic ultracold gases. They emphasized that the work opens new directions for quantum simulation, quantum computing and related disciplines that rely on precise control of many‑body states.
The project was highlighted by an Editor, CHEN Na, who framed it as a milestone for China in the global race to harness quantum matter. By demonstrating that counterflow superfluidity can be realized and controlled, the team provided a concrete platform where theorists can test ideas about multicomponent fluids, topological excitations and non‑equilibrium dynamics. That same platform is a natural candidate for implementing non‑Hermitian ingredients, such as controlled loss in one component or spatially patterned dissipation, which could bridge the gap between the newly discovered phase and experimentally accessible systems.
Two‑dimensional metals and the thin edge of superfluidity
While ultracold atoms offer a clean route to exotic superfluids, solid‑state systems are catching up by shrinking materials down to the atomic scale. Among the most celebrated advances this year was the realization of the First Ever Two Dimensional Metals, created by squeezing layered materials in a process that allows a single layer to behave as a genuine metal. A schematic of the vdW squeezing process, accompanied by an Image Credit to Nature, illustrates how van der Waals forces can be harnessed to stabilize these atomically thin conductors without the structural defects that usually plague ultra‑thin films.
These two‑dimensional metals are not superfluids in the strict sense, but they sit on the thin edge where strong correlations, reduced dimensionality and unusual band structures can give rise to superconductivity and other collective phenomena. In that context, the new non‑Hermitian superfluid phase offers a conceptual toolkit for thinking about how drive and dissipation might be used to manipulate transport in such systems. The broader survey of the 10 Most Significant Physics Breakthroughs in 2025 places these two‑dimensional metals alongside other breakthroughs that blur the line between traditional condensed matter and engineered quantum platforms, reinforcing the sense that materials science and quantum optics are converging on a shared frontier.
Why non‑equilibrium superfluids matter for technology
From a practical standpoint, the most important feature of the new superfluid phase is that it thrives in non‑equilibrium conditions where particles are constantly entering and leaving the system. That is precisely the regime where many quantum devices operate, whether they are superconducting qubits coupled to readout lines, exciton‑polariton condensates in microcavities or cold atoms subject to continuous measurement. If superfluid‑like coherence can be stabilized and controlled in such open environments, it could lead to more robust quantum sensors, low‑dissipation interconnects or even new architectures for quantum information processing that exploit, rather than fight, environmental coupling.
In particular, the sensitivity of the phase to lattice geometry suggests that device engineers could design structures where superfluid channels are routed along specific paths, shielded from loss in some regions and deliberately exposed in others to enable switching or readout. Combined with the lessons from counterflow superfluidity, where multiple components share the same space without friction, this opens the door to multiplexed quantum circuits in which different flows coexist and interact in controlled ways. The challenge will be to translate the idealized models into platforms that can be fabricated and operated at scale, a task that will likely draw on advances in nanofabrication, photonics and cold‑atom technology.
Theoretical puzzles and the road ahead
Despite the excitement, the discovery of a non‑Hermitian superfluid raises as many questions as it answers. One puzzle is how to define familiar concepts like superfluid density, critical velocity or vortices when the underlying Hamiltonian is not Hermitian and probability is not strictly conserved. Another is how universal the reported phase really is: does it require fine‑tuned parameters and specific lattice geometries, or is it a generic outcome of certain classes of gain‑loss patterns and interactions? Resolving these questions will require a combination of analytical work, numerical simulations and, crucially, experimental tests that can probe the predicted signatures.
On the experimental side, platforms that already realize non‑Hermitian physics, such as optical lattices with controlled loss, photonic crystals with asymmetric coupling or cold atoms with engineered dissipation, are natural candidates for hunting the new phase. The success of Chinese teams in realizing counterflow superfluidity in atomic ultracold gases shows that even delicate many‑body states can be stabilized and measured with high precision when the right tools are in place. If similar ingenuity is applied to non‑Hermitian designs, the next few years could see a wave of realizations that turn the current theoretical construct into a tangible state of matter, enriching the already crowded landscape of quantum fluids.
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