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Quantum 2020

Non-ergodic behavior due to Hilbert space shattering in tilted 1D Fermi-Hubbard chains

The 65th Annual Conference on Magnetism and Magnetic Materials (MMM 2020) was held in a virtual form. The COVID-19 pandemic, with its associated uncertainty about international travel and the ability to gather in large groups, meant that the Steering Committee decided to cancel the face-to-face meeting that had been planned in Palm Beach, Florida November 2-6, 2020.

We were reluctant to give up the benefits of meeting face-to-face, and know that shifting to a virtual conference is a significant change for this community. Nevertheless, we are first and foremost concerned about the health and safety of all our Conference participants and their loved ones on returning home after travelling.

The MMM 2020 Steering Committee was working exceptionally hard, along with our sponsors, the IEEE Magnetics Society and AIP Publishing, to make this event serve the needs of our participants, who live in time zones all around the globe, in the best possible way. 

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MMM 2020

invited talk

The Institute of Physics and IOP Publishing, in partnership with the Chinese Physical Society (CPS) and the University of Science and Technology of China (USTC) are proud to have brought together the international quantum science community online for this inaugural conference.


Early career and leading researchers from universities, industry and government worldwide came together to share, learn and collaborate on the latest research and emerging areas of high interest across quantum science and technology. The broad themes covered by Quantum 2020 included:

Quantum communication;
Quantum computing and quantum simulation;
Quantum sensing, metrology and imaging;
Quantum information theory, software and algorithms;
Quantum foundations;
Quantum technology in industry.
The four-day event featured talks from world-renowned scientists, interactive poster sessions and two exciting panel discussions on the themes of Quantum Technology in Industry and Quantum Technology Programmes Around the World.


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The Institute of Physics and IOP Publishing, in partnership with the Chinese Physical Society (CPS) and the University of Science and Technology of China (USTC) are proud to have brought together the international quantum science community online for this inaugural conference.

Early career and leading researchers from universities, industry and government worldwide came together to share, learn and collaborate on the latest research and emerging areas of high interest across quantum science and technology. 

We propose the novel method to calculate eigenenergies of quantum systems using Genetic Algorithms then Local search(GA then LS). It can calculate ground and excited energies in high accuracy. GA then LS is hybrid algorithm of Genetic Algorithms and local search algorithms such as newtonian methods e.g. Powell method. Genetic Algorithm(GA) is metaheuristic algorithms that solve problems by the lifecycle of creature, production, crossover, and inheritance. It can avoid local minimums in the case parameter landscapes don't have UV structure. GA then LS has been used to overcome such parameter landscapes that have UV structure. Variational Quantum Eigensolver(VQE) is very this case. Hence, calculating eigenenergies by this method using only GA or local search methods tend to be trapped by local minimums and failed. Therefore, we optimized the GA then LS for VQE method and calculated eigenenergies of some molecules. We call this new VQE method Genetic-Multi-Initial-Generalized VQE(GMIG-VQE).
In general, this algorithm applies local search every crossover process. But, local search may quite a short time. Besides, GA must take 100N generations for the number of parameters N. Therefore, we apply local search for chosen 10 parameter sets at the end of GA. 
We calculated the eigenenergies of some kind of molecules for four algorithms of local search; Conjugate Gradient, BFGS, Nelder-Mead, SLSQP methods. We will show the result of them and the ideas to improving this GMIG-VQE.

Proposal of Variational Quantum Eigensolver method using Genetic Algorithm then Local Search

Quantum sensing is inevitably one of the elegant examples for supremacy of quantum technologies over their classical counterparts. One of the desired endeavor of quantum metrology is ac field sensing. Here, by the means of analytical and numerical analysis, we show that many-body systems can be exploited efficiently for detecting the amplitude of an ac field. Due to the periodicity of the dynamics, any local block of the system saturates to a steady state which allows achieving precision for sensing the amplitude well beyond the classical limit. We associate the enhanced
quantum precision to closing of the Floquet gap, resembling the features of quantum sensing in the ground state of critical systems. Remarkably, the scaling of precision with respect to the number of resources becomes close to the Heisenberg limit, along the line where Floquet gap vanishes. This shows the potential of many-body systems for providing quantum enhanced precision in ac field sensing.

Many-body steady-state AC field quantum sensing

"Trapped ions are among the best-controlled quantum systems. However, for molecules, a similar degree of control currently lacks due to their complex energy-level structure. Quantum-logic protocols in which atomic ions serve as probes for molecular ions are a promising route for achieving this level of control. Here, I will describe our experimental results in achieving >99% fidelity in the quantum-nondemolition state detection of the nitrogen ion's electronic, vibration, and rotation ground state [1], thus making a crucial step towards the coherent manipulation of molecular quantum states. We further exploited our quantum-logic protocol for hyperfine and Zeeman resolved state identification and preparation in a complex region of the molecular spectrum, mimicking the situation encountered with polyatomic molecules [2]. The quantum control of rotation and vibration of molecules will open up opportunities for creating new time standards in the THz domain [3], searching new physics, improving molecular calculations, performing state-to-state controlled chemistry, and encoding quantum information in molecular qubits in quantum-computation and communication applications.

[1] Sinhal, Meir, Najafian, Hegi, Willitsch, Science 367, 1213 (2020).
[2] Najafian, Meir, Sinhal, Willitsch, arXiv:2004:05306 (2020).
[3] Najafian, Meir, Willitsch, arXiv:2007.11097 (2020)."

Quantum-logic state detection and preparation of rovibrational molecular states

"Protecting qubits from errors is mandatory to realize scalable quantum computing platforms. However, standard quantum error correction (QEC) codes based on multi-qubit encoding yield a large increase in the number of physical qubits and operations, thus making the control of such a platform very demanding.

Here we show that Molecular Nanomagnets can be used to easily overcome this limitation, by naturally embedding quantum error corrected units in a single multi-level molecule.

This is made possible by the rich and chemically tunable spectrum of these systems, characterized by many accessible levels with long coherence times. We perform a perturbative expansion of the Lindbald equation to design a scheme, based on such molecular qudits, which efficiently protects them from real errors, induced by pure dephasing. We then derive the sequence of pulses actually implementing QEC on a real spin system and demonstrate the effectiveness of our approach by numerical simulations.

We already get a remarkable gain (up to an order of magnitude) in the final error with a simple existing molecule consisting of a  nuclear qudit coupled to an electronic ancilla, used for error detection. This gain is further improved by scaling to larger spins, as we quantitatively analyze."

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Non-ergodic behavior due to Hilbert space shattering in tilted 1D Fermi-Hubbard chains

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Proposal of Variational Quantum Eigensolver method using Genetic Algorithm then Local Search

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