Quantum errors are a normal part of quantum computing because fragile physical qubits (the tiny components storing data) can easily break down because of environmental noise, like heat, stray signals or microscopic vibrations. Typical fixes involve vast amounts of extra hardware qubits, which make computers larger, more expensive and harder to build.
Making quantum errors easier to detect
In a paper published in the journal Nature, scientists report developing a two-qubit entangling gate that automatically flags its most common errors as they occur.
The team at D-Wave Quantum Inc. engineered an ultrafast link, called a controlled-Z (CZ) entangling gate, that entangles two qubits in just 500 nanoseconds. When errors occur, the system automatically flags most of them as photon losses (known as erasures) instead of letting them turn into hidden glitches.
The hardware works by splitting each qubit across two tiny superconducting microwave cavities. To make them interact, the scientists briefly shifted a photon into a central bridge, waited for the interaction to occur and then shifted the light back to its starting place.
In previous attempts to build entangling gates for specialized qubits, connecting two qubits often broke their built-in error detection, turning easy-to-spot mistakes back into hidden glitches. Here, hidden does not mean completely invisible to scientists but rather that the computer fails to catch the error live during a calculation.
To test their gate, the paper's authors built an entangled two-qubit state and ran random sequences of operations. They then counted how many errors were automatically flagged versus hidden.
The tests revealed that about 0.5% of operations produced detectable photon losses that were automatically flagged. Remaining hidden errors were below about 0.1% per gate, while bit-flip errors (disastrous glitches that accidentally knock a qubit from state 0 into a state 1, or a state 1 into a state 0) were extremely rare, around 1 in 1 million.
As the authors state, "Our experimental demonstration confirms that the error hierarchy is largely preserved during the gate." In other words, the system preserved its error-detection ability, ensuring that most errors were flagged.
Scaling up
Although the control qubit takes on slightly more stress during the process than the target qubit, computer simulations revealed a major advantage. By keeping failures flagged rather than hidden, larger quantum computers built from these qubits should be able to suppress errors much more effectively as they grow in size. "These results enable a faster path to error-corrected systems that rapidly suppress errors as they scale."
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Publication details
An entangling gate for dual-rail erasure qubits, Nature (2026). DOI: 10.1038/s41586-026-10822-y
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Citation: Two-qubit entangling gate flags its own errors as detectable photon losses (2026, August 6) retrieved 6 August 2026 from https://phys.org/news/2026-08-qubit-entangling-gate-flags-errors.html
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