Quantum Particle Defies the Law of Friction express
In ordinary environments, a body slows down due to friction. But in the quantum world, there is superfluidity: liquids flow without loss, like the famous helium at ultra-low temperatures. Previously, it was considered unthinkable for this to happen in a chain of particles — a one-dimensional system. However, physicists launched a foreign atom into a row of ultracold atoms. Like a bead passing through others strung on a thread: a free gap instantly appears ahead of it, and the chain closes up behind — without the slightest resistance. Even at supersonic speeds. An unexpected twist: the slower the initial push, the longer the braking lasted before uniform sliding. But ultimately, the motion always became perpetual and effortless. In the ordinary world, friction generates heat and disorder, but here — not a hint. This promises devices that transmit information without any loss.
Original abstract
as written by the authors arXiv:2602.12320
The frictionless motion of an object through a fluid medium is commonly viewed as a hallmark of superfluidity. According to Landau, kinematic constraints prohibit superfluid behavior in one-dimensional (1D) bosonic systems. Here, using ultracold atoms, we show how a microscopic impurity can propagate through a strongly interacting 1D Bose gas without any friction, at odds with conventional expectations. We inject the impurity with initial velocities ranging from the subsonic to supersonic regime, and subsequently track its dynamics. For supersonic initial velocities, we observe the formation of a shock wave and a remarkably fast relaxation to a stationary regime, on a time scale that increases with decreasing impurity velocity. After reaching the stationary state, the impurity continues its motion through the system with a finite velocity. Our findings demonstrate how quantum effects can conspire to eliminate dissipation of a microscopic object immersed in a quantum fluid, thereby bringing novel insights into the propagation of matter and information in the quantum realm.
If water could flow without friction, a thrown stone would create eternal ripples, and water in a river would never stop.