Los investigadores han utilizado qubits de espín de luz y electrones para controlar el espín nuclear en material 2D, abriendo una nueva frontera en la ciencia y la tecnología cuánticas. Crédito: Second Bay Studio
Una red 2D de qubits de electrones y espín nuclear abre una nueva frontera en la ciencia cuántica.
Los investigadores han abierto una nueva frontera en la ciencia y la tecnología cuánticas mediante el uso de fotones y qubits de espín de electrones para controlar los espines nucleares en material bidimensional. Esto permitirá aplicaciones como la espectroscopia de resonancia magnética nuclear a escala atómica y la capacidad de leer y escribir información cuántica con espines nucleares en materiales 2D.
Como se publicó hoy (15 de agosto) en Materiales naturalesel equipo de investigación de la Universidad de Purdue utilizó qubits de espín de electrones como sensores a escala atómica y también para realizar el primer control experimental de qubits de espín nuclear en nitruro de boro hexagonal ultrafino.
«Este es el primer trabajo que muestra la inicialización óptica y el control coherente de los giros nucleares en materiales 2D», dijo el autor correspondiente Tongcang Li, profesor asociado de física y astronomía e ingeniería eléctrica e informática de Purdue, y miembro del Instituto de Ingeniería y Ciencia Cuántica de Purdue. .
“Ahora podemos usar la luz para inicializar giros nucleares y con este control podemos escribir y leer información cuántica con giros nucleares en materiales 2D. Este método puede tener muchas aplicaciones diferentes en memoria cuántica, detección cuántica y simulación cuántica.
La tecnología cuántica se basa en el qubit (bit cuántico), que es la versión cuántica de un bit informático clásico. En lugar de un transistor de silicio, a menudo se construye un qubit con un[{» attribute=»»>atom, subatomic particle, or photon. In an electron or nuclear spin qubit, the familiar binary “0” or “1” state of a classical computer bit is represented by spin, a property that is loosely analogous to magnetic polarity — meaning the spin is sensitive to an electromagnetic field. To perform any task, the spin must first be controlled and coherent, or durable.
The spin qubit can then be used as a sensor, probing, for example, the structure of a protein, or the temperature of a target with nanoscale resolution. Electrons trapped in the defects of 3D diamond crystals have produced imaging and sensing resolution in the 10-100 nanometer range.
However, qubits embedded in single-layer, or 2D materials, can get closer to a target sample, offering even higher resolution and stronger signal. Paving the way to that goal, the first electron spin qubit in hexagonal boron nitride, which can exist in a single layer, was built in 2019 by removing a boron atom from the lattice of atoms and trapping an electron in its place. So-called boron vacancy electron spin qubits also offered a tantalizing path to controlling the nuclear spin of the nitrogen atoms surrounding each electron spin qubit in the lattice.
In this work, Li and his team established an interface between photons and nuclear spins in ultrathin hexagonal boron nitrides.
The nuclear spins can be optically initialized – set to a known spin – via the surrounding electron spin qubits. Once initialized, a radio frequency can be used to change the nuclear spin qubit, essentially “writing” information, or to measure changes in the nuclear spin qubits, or “read” information. Their method harnesses three nitrogen nuclei at a time, with more than 30 times longer coherence times than those of electron qubits at room temperature. And the 2D material can be layered directly onto another material, creating a built-in sensor.
“A 2D nuclear spin lattice will be suitable for large-scale quantum simulation,” Li said. “It can work at higher temperatures than superconducting qubits.”
To control a nuclear spin qubit, scientists began by removing a boron atom from the lattice and replacing it with an electron. The electron now sits in the center of three nitrogen atoms. At this point, each nitrogen nucleus is in a random spin state, which may be -1, 0, or +1.
Next, the electron is pumped to a spin-state of 0 with laser light, which has a negligible effect on the spin of the nitrogen nucleus.
Finally, a hyperfine interaction between the excited electron and the three surrounding nitrogen nuclei forces a change in the spin of the nucleus. When the cycle is repeated multiple times, the spin of the nucleus reaches the +1 state, where it remains regardless of repeated interactions. With all three nuclei set to the +1 state, they can be used as a trio of qubits.
Reference: “Nuclear spin polarization and control in hexagonal boron nitride” by Xingyu Gao, Sumukh Vaidya, Kejun Li, Peng Ju, Boyang Jiang, Zhujing Xu, Andres E. Llacsahuanga Allcca, Kunhong Shen, Takashi Taniguchi, Kenji Watanabe, Sunil A. Bhave, Yong P. Chen, Yuan Ping and Tongcang Li, 15 August 2022, Nature Materials.
DOI: 10.1038/s41563-022-01329-8
At Purdue, Li was joined by Xingyu Gao, Sumukh Vaidya, Peng Ju, Boyang Jiang, Zhujing Xu, Andres E. Llacsahuanga Allcca, Kunhong Shen, Sunil A. Bhave, and Yong P. Chen, as well as collaborators Kejun Li and Yuan Ping at the University of California, Santa Cruz, and Takashi Taniguchi and Kenji Watanabe at the National Institute for Materials Science in Japan.
“Nuclear spin polarization and control in hexagonal boron nitride” was published with support from Purdue Quantum Science and Engineering Institute, DARPA, National Science Foundation, U.S. Department of Energy, Office of Naval Research, Tohoku AIMR and FriDUO program, and JSPS KAKENHI.