Quantum computing promises to revolutionize problem-solving, but maintaining the delicate quantum states of qubits remains a significant challenge. A recent experiment using ytterbium ions and Fibonacci-sequenced laser pulses offers a promising new approach to extending the lifespan of these quantum bits.
Quantum computers leverage the unique properties of qubits, which can exist in a superposition of states (both 0 and 1 simultaneously). This allows them to explore multiple solutions to a problem concurrently, offering a substantial speed advantage over classical computers. However, qubits are extremely sensitive to environmental disturbances like temperature fluctuations and electromagnetic fields. These disturbances can cause decoherence, disrupting the entangled state and jeopardizing computations.
The experiment, conducted by researchers using a Quantinuum quantum computer, focused on 10 ytterbium ions as qubits. These ions were controlled by electric fields and manipulated with laser pulses. Initially, periodic laser pulses maintained the qubits’ entangled state for 1.5 seconds. However, when the laser pulses followed the Fibonacci sequence, a remarkable improvement was observed. The edge qubits, those furthest from the center of the configuration, remained entangled for the entire 5.5-second duration of the experiment. This suggests the Fibonacci sequence could significantly extend the coherence time, potentially even beyond the observed 5.5 seconds.
The Fibonacci sequence, where each number is the sum of the two preceding ones (e.g., 1, 1, 2, 3, 5), creates a quasi-periodic pattern in the laser pulses. This quasi-periodicity, analogous to the structure of quasicrystals, appears to be key to the enhanced coherence.
“The key result was demonstrating the difference between periodic and Fibonacci-sequenced pulses and how the latter provided superior protection against errors,” explained Justin Bohnet, a quantum engineer at Quantinuum and co-author of the study.
Lead author Philipp Dumitrescu, a quantum physicist who conducted the research while at the Flatiron Institute, elaborates: “By using quasi-periodic sequences based on the Fibonacci pattern, the system behaves as if there are two distinct directions of time.” This “time-translation symmetry,” where experimental outcomes remain consistent regardless of the time of execution, contributes to the robustness of the quantum state.
The Fibonacci-sequenced pulses create a complex evolution that effectively cancels out errors affecting the edge qubits, preserving their quantum coherence for extended periods. This is akin to projecting higher-dimensional symmetries onto a lower dimension, similar to the patterns in Penrose tilings.
The findings, published in Nature, highlight the potential of Fibonacci-sequenced laser pulses for mitigating decoherence and extending the lifespan of quantum states. This advancement is crucial for realizing the full potential of quantum computing. By enhancing the robustness and longevity of quantum systems, this technique paves the way for more complex and computationally intensive quantum algorithms.
Further research will explore the underlying mechanisms and optimize this technique for various quantum computing platforms. The ability to maintain quantum coherence for longer durations represents a significant step towards building practical and powerful quantum computers.
Nature Article
Fibonacci Sequence
Simons Foundation Release
Penrose Tiling
