Quantum Couple Makes Molecular Qubits Stick Around Longer based on CIQTEK EPR100

Margaret Harris, the editor of the industry section of Physics World, tweeted (@DrMLHarris) about a Chinese "quantum couple", Dr. Yingqiu Dai and Dr. Zhifu Shi. As the first and third authors respectively, they published an important scientific achievement: based on the experimental results using CIQTEK X-band pulse electron paramagnetic resonance (EPR or ESR) spectroscopy EPR100, they improved the coherence time of quantum bits to 1.4 ms and increased the quality factor of quantum bits by 40 times!

The editor of Physics World, Isabelle Dumé, reported the scientific achievements of the Key Laboratory of Microscopic Magnetic Resonance, Chinese Academy of Sciences, in the direction of molecular quantum bits research under the title "Molecular qubits stick around for longer". This major breakthrough was published in the authoritative academic journal, Chinese Physics Letters, under the title of "Experimental Protection of the Spin Coherence of a Molecular Qubit Exceeding a Millisecond", and attracted wide attention in the academic field.

- Link to the paper in Chinese Physics Letters (Yingqiu Dai, Yue Fu, Zhifu Shi et al 2021 Chin. Phys. Lett. 38 030303): http://cpl.iphy.ac.cn/10.1088/0256-307X/38/3/030303

- Link to Physics World reporthttps://physicsworld.com/a/molecular-qubits-stick-around-for-longer

It is worth mentioning that the CIQTEK X-band pulse EPR (ESR) spectroscopy EPR100 used in the experiment was designed by Dr. Yingqiu Dai's fiancé, Dr. Zhifu Shi.

Dr. Yingqiu Dai and Dr. Zhifu Shi were using CIQTEK EPR100 for scientific research

Dr. Yingqiu Dai and Dr. Zhifu Shi were using CIQTEK EPR100 for scientific research

"CIQTEK X-band pulsed EPR (ESR) spectrometer plays a crucial role in the research process. Traditional commercial scientific instruments, affected by parameters such as the phase stability of the amplifier and the maximum number of pulses, cannot meet the needs of the experimental protocol. So the research team improved on the existing EPR spectrometer technology in the laboratory and completed the independent development of an arbitrary sequence generator, microwave pulse amplifier, and other components to complete a brand new X-band pulsed EPR (ESR) spectrometer that meets the experimental requirements. The final instrument can generate more than 10,000 high-precision pulse sequences with an accuracy of 50 ps, generating high-phase stability and high-intensity microwave pulses acting on quantum bits to finally complete the work." Dr. Zhifu Shi said.

Extended Coherence Time Allows Quantum Technology to be Used More Widely

In recent years, quantum computing has become a revolutionary technology. By taking advantage of the superposition and entanglement of quanta, quantum computers can accomplish in just a few seconds what classical computers cannot do in years for some specific scientific problems. And the longer the coherence time of quantum bits, the stronger the performance of quantum computing. However, quantum systems in the environment inevitably interact with vibrations, temperature fluctuations, electromagnetic waves, etc., resulting in the loss of coherent information to the environment (often called "decoherence"), which disrupts the long time quantum computing process and greatly limits the realization of complex quantum tasks, plaguing countless scientists. Therefore, it is crucial to reduce the decoherence caused by the interaction between quantum bits and the environment.

The common candidate systems currently used as quantum bits are optical systems, superconductors, ion traps, solid material defects, and quantum dots. The electron spin of magnetic molecules is an emerging system for quantum computing. Compared with other systems, this quantum bit can be tuned and modified the molecular structure more easily by chemical synthesis and can be synthesized in large quantities. The regular arrangement to create quantum circuits is also relatively easy.

However, like other quantum bits, the superposition state of this quantum bit is fragile. Although scientists have used many methods, such as dilution of antimagnetic compounds, rigidity enhancement of molecules during synthesis, and isotropic purification, to reduce the effect of environmental noise on the coherence of magnetic molecular quantum bits, the coherence time of such molecular quantum bits has not exceeded 1 ms so far.

CIQTEK X-Band Pulse EPR (ESR) Spectroscopy EPR100

CIQTEK X-Band Pulse EPR (ESR) Spectroscopy EPR100

To extend the coherence time, a research team from the University of Science and Technology of China used the electron spin of the transition metal coordination compound (PPh4)2[Cu(mnt)2] as a quantum bit on a CIQTEK X-band pulsed EPR (ESR) spectroscopy EPR100 and applied microwave pulses to "flip" the quantum state of the molecular quantum bit ", averaging out the effect of a specific coupling in a specific time. Their study has extended the coherence time of the quantum bit from 6.8 µs to 1.4 ms. This time can theoretically support 145,000 basic logic operations. This is called the "quality factor (i.e., the ratio of coherence time to manipulation time)" of the quantum bit, and is a 40-fold improvement over the previously reported value.

Screenshot of the Paper

Screenshot of the Paper

According to Dr. Yingqiu Dai, the work used a microwave pulse sequence manipulation method that did not require special modifications to the molecule compared to traditional methods, preserving the possibility of other spins being utilized as quantum bit resources.

This research result is significant, not only can greatly improve the capability of quantum computing but also can be widely used in the field of magnetic biomedical imaging and quantum sensing.

CIQTEK EPR (ESR) Spectroscopy

Originating from the Key Laboratory of Microscopic Magnetic Resonance of the Chinese Academy of Sciences at the University of Science and Technology of China, CIQTEK has been deeply engaged in the field of high-end scientific instruments such as electronic paramagnetic resonance (EPR) spectroscopy for more than ten years, and has now launched a comprehensive X-band series for commercial use, and has successfully advanced to W-band high-frequency EPR (ESR) spectroscopy. 

EPR (ESR) spectroscopy is a method to study the structure, dynamics, and spatial distribution of unpaired electronics. It can provide in-situ and non-destructive information on electron spins, orbitals, and nuclei at the microscopic scale. They are particularly useful for studying metal complexes or free radicals.