Harvard researchers Mikhail Lukin and Julia Semegini led a team that first observed an exotic state of matter called quantum spin fluid.
Scientists from Harvard have observed a new state of matter for the first time in the world. The hypothesis of its existence was put forward by other scientists almost 50 years ago. We are talking about a quantum spin liquid, which has great potential. For example, it can be used for quantum computing.
For materials to become magnetic, the electron spins in it must be highly ordered. The most common type of magnetism (which holds the magnet on the refrigerator) works because the spins of all the electrons in the material are oriented in the same direction. Other types of magnetism can occur when the spins of adjacent electrons alternate up and down in a cage. In other words, everything works as long as there is order in the material.
But in 1973, physicist Philip Anderson put forward a hypothesis about the state of matter, which is called quantum spin fluid. Its peculiarity is that it does not obey the standard rules of magnetism. When the material cools, it does not form a solid and, importantly, their electrons are not stabilized in a highly ordered state. Instead, they will constantly switch, entangling themselves with each other in a complex quantum state.
A group of scientists led by Harvard created and observed quantum spin liquid for the first time. To do this, the researchers used a programmable quantum simulator they developed several years ago, which uses lasers to hold 219 atoms in a grid. The properties of these atoms can be carefully modified, including the spins of their electrons.
For this study, the team organized the atoms into a triangular lattice, which means that each has two nearest neighbors. A pair of electrons can be magnetically stabilized one way or another, because their spins can either coincide or alternate, but the presence of a third wheel upsets this balance, creating a “frustrated magnet” that cannot settle.
The resulting quantum spin fluid exhibits several useful quantum phenomena. First, entanglement, when atoms can influence each other over great distances and even “teleport” information. Second, quantum superposition, when atoms can exist in several states at the same time. Both are useful for building quantum computers that need to be more robust against external interference.
“This is a special moment for science. Now we can literally touch the quantum spin fluid, manipulate its state and study its properties. In essence, this is a state of matter unknown to us, which has never been observed in the past, ”said Mikhail Lukin, a professor at Harvard University, whose words are quoted by the university’s press service.
Having confirmed the existence of a quantum spin liquid, Professor Lukin and his colleagues studied its physical properties, and also tried to adapt this form of matter to create quantum memory cells that are protected from most external interference. The first preliminary experiments, according to the researchers, convinced them that this was possible in practice. The research is published in the journal Science.