Scientists say they’ve reached a “critical turning point” after developing technology that makes silicon-based quantum processors more cost effective.
Quantum computing company Equal1 has created a quantum processing unit (QPU) that can be built using conventional semiconductor manufacturing processes. This negates the complexity and costs typically related to producing quantum processors using exotic materials or complex techniques.
The company also developed what its representatives called “the most complex quantum controller system ever developed.” This chip can operate at very low temperatures and paves the best way for millions of qubits on a single chip, which implies it can concurrently handle huge numbers of quantum bits of information while maintaining their stability and accuracy for computation.
By contrast, today’s strongest quantum chips contain only 1000’s of qubits and are made of superconductors, all requiring cooling to near absolute zero to perform quantum computations.
Overall, new technologies “are paving the way to the next stage quantum computing and we have demonstrated that the fastest way to scale is to use existing silicon infrastructure,” said Equal1 wa statement.
Quantum impracticality
Building quantum chips is an extremely difficult and expensive process. Unlike regular computer chips, which use binary bits to process information in the form of ones or zeros, quantum chips use qubitsthat are based on principles quantum mechanics.
Qubits have special properties that allow them to exist in multiple states at once – a phenomenon called superposition – and work together in ways that traditional bits cannot, in a process called entanglement. The resulting parallel processing enables quantum computers to solve problems far beyond the capabilities of classical systems.
However, qubits are extremely delicate. They only work if they are kept in a state of coherence, which means they maintain their quantum state long enough to perform calculations. Coherence is easily disrupted by environmental factors such as temperature changes or electromagnetic noise – hence the need to use very low temperatures to avoid interference.
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Typically, quantum chips are also made using exotic or custom-made materials such as superconducting metals, which require expensive and complex manufacturing processes. Equal1’s innovation is the use of silicon – one of the most abundant and widely used materials in the semiconductor industry.
Silicon provides a stable environment for qubits, especially when using a mixture of materials called silicon germanium (SiGe). In a study published on December 2 in the preprint database arXivEqual1 scientists explained that SiGe combines the stability of silicon with the ability of germanium to increase electronics performance, making it ideal for quantum applications. More importantly, SiGe chips can be manufactured using the same processes and factories already used to produce traditional computer chips, potentially creating quantum processors cheaper and easier to scale.
Equal1 officials said the 6-qubit SiGe array – the part of the chip where qubits are created and controlled – has achieved breakthroughs in two key areas: the precision of quantum gate operations and the speed at which these operations are performed.
Specifically, the chip demonstrated a single-qubit gate fidelity of 99.4% at an operating speed of 84 nanoseconds and a two-qubit gate fidelity of 98.4% at a speed of 72 nanoseconds. The high accuracy of quantum gates minimizes errors in calculations, and faster gate speeds reduce the risk of qubits losing their quantum properties during operation. These factors determine the accuracy of quantum calculations and the ability of qubits to maintain their quantum states long enough to complete complex operations.
“This result demonstrates the enormous advantages of silicon qubits – the ability to achieve the performance required to scale in two key areas – quantum gate fidelity and speed.” – Nodar Samkharadze, chief quantum architect at Equal1, said in a statement.
We’re winding it up
To ensure reliable quantum operations, the Equal1 device uses “spin qubits”. Spin qubits encode information spin state of the electron. In their study, the researchers found that spin qubits are particularly well-suited for integration with silicon because silicon provides a stable environment for electron spins. This reduces the danger of qubits losing their delicate quantum properties due to interference from the environment.
Equal1 also developed a quantum controller chip that uses a multi-board architecture; this design divides the chip into multiple boards that can operate semi-independently. This architecture is vital to scaling quantum systems since it allows control functions to be distributed throughout the chip, avoiding bottlenecks that can occur when counting on a single processing unit.
The controller operates at a temperature of 300 millikelvin, which is barely higher absolute zero — which allows it to manage qubits efficiently while maintaining the conditions needed for coherence. Equal1 officials said the controller also features artificial intelligence (AI)-based error correction technology for real-time adjustments that maintains the soundness and accuracy of quantum operations.
“Today marks a critical turning point for Equal1 and the quantum computing industry,” Elena Blokhina, the corporate’s chief scientific officer, added in a statement. “Equal1 has always believed that silicon is the enabler for scaling quantum computing, and today, with world-leading results in qubits and control chips, we have taken an important step towards that vision.”
