Purdue University researchers have unlocked a new area of quantum science and technology by using photons and electron spin qubits to tune nuclear spins in a two-dimensional material. They used electron spin qubits as atomic-scale sensors to perform the first experimental control of nuclear spin qubits in ultrathin hexagonal boron nitride. The study could lead to applications such as atomic-scale nuclear magnetic resonance spectroscopy. It could also allow quantum information to be read and written by nuclear spins in two-dimensional materials. Corresponding author Tongcang Li, associate professor of physics, astronomy, and electrical and computer engineering at Purdue, said, “This is the first work to show optical initialization and coherent control of nuclear spins in 2D materials. Now we can use light to initialize nuclear spins, and with this control, we can write and read quantum information with nuclear spins in two-dimensional materials. This method can have many different applications in quantum memory, quantum sensing and quantum simulation.” Scientists have for the first time created an interface between photons and nuclear spins in ultrathin hexagonal boron nitride. The surrounding electron spin qubits can optically initialize the nuclear spins or set them to a known spin. Once initialized, a radio frequency can be used to “write” information by changing the nuclear spin qubit, or “read” information by measuring the changes in nuclear spin qubits. Their technique uses three nitrogen atoms simultaneously and has coherence periods more than 30 times longer than those of electron qubits at room temperature. Additionally, a sensor can be embedded in the 2D material by physically placing it on top of another material. Li said, “A two-dimensional nuclear spin lattice will be suitable for large-scale quantum simulation. It can operate at higher temperatures than superconducting qubits.” The researchers started by removing a boron atom from the lattice and replacing it with an electron to control a nuclear spin qubit. Three nitrogen atoms surround the electron at this time. Each nitrogen nucleus is currently in a random spin state, which can be either -1, 0, or +1. The electron is then pumped into the spin 0 state with laser light, which has a negligible effect on the spin of the nitrogen nucleus. Finally, an ultrafine interaction between the excited electron and the three surrounding nitrogen nuclei causes a change in the nucleus’s spin. When the cycle is repeated many times, the nuclear spin reaches the +1 state, where it remains independent of repeated interactions. With the three cores set to the +1 state, they can be used as a trio of qubits. Journal Reference:
