Quantum Computing System Halt in Quantum Computer

Related Vendors

Helmholtz-Zentrum Dresden- Rossendorf e.V. Bibliothek

SIMTOS (Seoul International Machine Tool Show)

Quantum computers promise enormous computing power. However, researchers at the Helmholtz-Zentrum Dresden-Rossendorf (Germany) are now warning about the Quantum Zeno Effect: With an increasing number of qubits, even tiny environmental disturbances can completely freeze the computing process.

For engineers, it resembles the ultimate system crash: A complex control task is running, but the system suddenly freezes. What in classical automation technology is usually attributed to software errors or overload now emerges as a fundamental physical obstacle in the development of future supercomputers.

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have discovered that so-called adiabatic quantum computers become extremely sensitive to the smallest disturbances as scaling increases – and in extreme cases, they simply come to a halt.

When the Energy Landscape Tips

Quantum computers are considered promising for tasks where classical computers fail, such as massive logistics optimizations or material simulations. One promising architecture is adiabatic quantum computers. Their principle: the computing units (qubits) continuously remain in the state of lowest energy (ground state). "Programming" occurs by altering the energy landscape of the qubits from the outside extremely slowly and continuously. At the end of this transformation, the new ground state provides the solution.

This approach is considered hardware-independent, robust, and relatively elegant. However, Dr. Gernot Schaller and Prof. Ralf Schützhold from the HZDR Institute for Theoretical Physics have identified a blind spot when scaling these systems.

A quantum computer can only compute successfully if its qubits are not overly disturbed.

Prof. Ralf Schützhold, Director of the Institute of Theoretical Physics at HZDR

The Quantum Zeno Effect or the Problem with the Oven Door

To maintain the delicate superposition and entanglement of the qubits, quantum computers are massively shielded and cooled to near absolute zero (-273.15 °C / -459.67°F). Nevertheless, environmental influences can never be completely excluded. The tricky part: The more qubits are interconnected, the finer the changes in the energy landscape become.

From a certain scaling size, the so-called Quantum Zeno Effect kicks in. Tiny electromagnetic disturbances act on the system like an unintended "measurement" from the outside—and halt the evolution of the quantum state.

The researchers compare this phenomenon to baking a cake: A cake needs to rise undisturbed in the oven. Constantly opening the oven door to check if it is done interrupts the process—the dough collapses. The same happens to the computation process in a quantum computer: With too many small disturbances, the system never reaches its final state, and the calculation freezes.

Quantum Computing

Use of Quantum Computers in Industrial Simulation

Active Disturbance Compensation as a Solution

As is common in automation technology, disturbances require not only passive but also active countermeasures. Purely physical shielding ("padlock on the oven") is no longer sufficient for future large-scale quantum computers. Prof. Schützhold therefore proposes the "spin-echo method": by targeted, coherent counterpulses, the disruptive coupling of qubits to their environment can be actively reduced. In the cake metaphor, this corresponds to a high-tech oven that compensates for the temperature drop when the door is opened with an immediate, ultra-fast heating pulse.

For future hardware development, this means that a robust quantum computer can only be successfully scaled if disturbance management for the Quantum Zeno Effect is already firmly anchored in the system design ("Security by Design").

Out of Its Infancy!

The Quantum Computer Becomes an Economic Factor