- ETH Zurich quantum chip sees superconducting qubit act as CPU and the vibrational states of a fingernail-width acoustic resonator serve as quantum RAM
- The approach borrows from classical computer architecture as it completely flips the script on how modern quantum computers can store short-term data
- The team demonstrated a universal gate set and ran small instances of the quantum Fourier transform and period finding
A guitar string essentially stores a note based on how it vibrates, and plucking it differently will play a completely different note.
A team of researchers at ETH Zurich has exploited the same principle to build a quantum chip that stores information by replacing the string with microscopic acoustic resonators.
This allows the chip to significantly increase its working memory, essentially greatly increasing storage capacity, a prohibitively expensive commodity in quantum computing.
A vibration based quantum storage game
ETH Zurich’s research is led by quantum physicist Yiwen Chu, who used tiny mechanical vibrations to both store and process information. However, the vibrations go far beyond the range of human hearing and occur inside a quantum chip, where they essentially replace or supplement the working memory of a quantum computer.
The study, published by the Hybrid Quantum Systems group, lists Professor Yiwen Chu along with PhD students Yu Yang and Igor Kladarić as lead authors and focuses on replicating the division of labor seen in a classical computer.
A superconducting transmon qubit serves as the CPU, while the working memory (the quantum equivalent of RAM) is a high-harmonic bulk acoustic wave resonator, or HBAR, whose many vibrational modes each serve as a memory slot.
The qubit essentially switches a quantum state from a vibrational state (reads it in classical computing terms), manipulates it (modifies it) and switches it back (writes it). This provides a unique configuration that most modern quantum computers do not follow, where processing and storage are two separate segments; most designs treat both memory and computing in the same way.
However, the approach has advantages: acoustic waves have wavelengths roughly a hundred thousand times shorter than electromagnetic ones, which allows an entire quantum chip to be extremely small, the research team says, even though the actual computer will be many orders of magnitude larger.
The chip has passed stress tests, including a proof of feasibility, which also included tests using two of the most commonly used methods to benchmark a quantum computer: the quantum Fourier transform and a period-finding algorithm.
The endgame here, as noted by the research team, is quantum random-access memory (QRAM), which would give modern quantum computers access to a much larger store of quantum memory than current specifications allow. Whether this succeeds depends on both the scalability of the approach and the computing power involved.
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