The problem of finding effective counterdiabatic drives for preparing ground states is related to finding good polynomial approximations of the inverse function. Credit: Jernej Rudi Finzgar.

Quantum ground states are the states at which quantum systems have the minimum possible energy. Quantum computers are increasingly being used to analyze the ground states of interesting systems, which could in turn inform the design of new materials, chemical compounds, pharmaceutical drugs and other valuable goods.

The reliable preparation of quantum ground states has been a long-standing goal within the physics research community. One quantum computing method to prepare ground states and other desired states is known as adiabatic state preparation.

This is a process that starts from an initial Hamiltonian, a mathematical operator that encodes a system’s total energy and for which the ground state is known, gradually changing it to reach a final Hamiltonian, which encodes the final ground state.

To accelerate adiabatic state preparation, physicists can use a method known as counterdiabatic driving. This technique works by adding an auxiliary term to a Hamiltonian that prevents the system from undergoing undesired excitations into higher energy states.

Researchers at Technical University Munich, Harvard University and Flatiron Institute recently introduced a new counterdiabatic driving method that could overcome some of the limitations of previously introduced techniques, providing rigorous performance guarantees.

Their proposed method, outlined in a paper published in Physical Review Letters, could be used to reliably and rapidly prepare the quantum ground states of quantum systems that vary in size and complexity.

“Ground state preparation is a fundamental task with applications in quantum many-body physics, quantum computation and even for solving combinatorial optimization problems,” Jernej Rudi Finzgar, first author of the paper, told Phys.org.

“Counterdiabatic driving is a widely adopted method that promises to speed up conventional, adiabatic, state preparation protocols. In this paper we set out to understand how much resources are required to implement such schemes.”

A promising alternative to conventional counterdiabatic methods

Most previously introduced counterdiabatic driving methods work by performing calculations that grow exponentially as systems become bigger or have variational approximations based on adjustable parameters. While the first of these approaches can be computationally intensive and harder to scale to larger systems, the second is often unreliable for the preparation of ground states.

Finzgar and his colleagues set out to develop a new counterdiabatic driving technique that does not rely on increasingly complex calculations or system-specific assumptions. Ultimately, they realized that the parameters that one needs to set in a variational approach are directly linked to a function approximation problem.

“Our approach relies on the fact that, at its core, crafting an effective counterdiabatic driving scheme boils down to the conceptually much simpler problem of fitting polynomials to the inverse function,” explained Finzgar.

“This effectively means that the parameters of the proposed counterdiabatic driving scheme do not depend on the microscopic details of the system and are therefore, in a sense, universal across a variety of systems.”

Initial results and extension to larger systems

“The most important finding of our work is probably that we determined how the cost of implementing counterdiabatic driving schemes is for a given ground state preparation task,” said Finzgar.

“Additionally, and counterintuitively, we find that sometimes the performance is limited by properties of states of the system that are far away in energy from the ground state that we are trying to prepare. This is at odds with conventional wisdom that the cost of ground state preparation is determined by the low energy properties of the system.”

Universal CD driving at finite timescales. Credit: Physical Review Letters (2025). DOI: 10.1103/pqhl-nbtk

Due to the high-frequency properties of the system, the originally proposed scheme breaks down when the systems are increased to large sizes. To remedy this, Finzgar and his colleagues showed that when combined with finite-time adiabatic protocols, their proposed technique could be applied to very large quantum systems.

Moreover, they found that in practice their approach allowed them to prepare ground states more rapidly and reliably than the conventional counterdiabatic driving approaches they compared it to.

The new method devised by this team of researchers has so far proved to be a viable and scalable alternative to conventional counterdiabatic driving techniques. In the future, it could be used to prepare the ground state of various quantum systems, which could have important implications for quantum computing, quantum simulation and materials design.

“My future research plans in this area will include finding new efficient implementations of our counterdiabatic driving scheme on the rapidly advancing quantum devices,” added Finzgar.

Written for you by our author Ingrid Fadelli, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You’ll get an ad-free account as a thank-you.

More information: Jernej Rudi Finžgar et al, Counterdiabatic Driving with Performance Guarantees, Physical Review Letters (2025). DOI: 10.1103/pqhl-nbtk.

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Citation: Quantum ground states: Scalable counterdiabatic driving technique enables reliable and rapid preparation (2025, November 22) retrieved 22 November 2025 from https://phys.org/news/2025-11-quantum-ground-states-scalable-counterdiabatic.html

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