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Quantum Error Correction

What is quantum error correction, and why is it important?

Quantum error correction is a set of techniques used to protect the information stored in qubits from errors and decoherence caused by noise.

Quantum computers today have high error rates – around 1 error occurs in 1000 operations before failure. For quantum computers to be useful, error rates need to be as low as 1 in a trillion. A huge improvement in performance is needed, however proven progress is already happening in the community.

We are focussed on breaking though this fundamental challenge by building the quantum error correction stack, and by understanding optimal quantum algorithms for error corrected quantum computers.

Building the Quantum Error Correction Stack

"If you don't solve error correction, then you'll never have a useful quantum computer"

- Earl Campbell, Head of Architecture

Why is quantum error correction such a tough challenge to crack?

Qubits, the building blocks of quantum computers, are extremely sensitive to environmental disturbances. The slightest change in temperature, or any interactions with surrounding molecules could cause a qubit to lose its information. Not only this, but millions of qubits are needed to perform useful calculations.

As such, powerful decoders are required to detect and correct errors with complete accuracy, and at incredible speeds.

Quantum error correction at scale


Riverlane Roadmap: Three basic steps to decoder success

Decoding in real-time is a huge challenge for fast quantum computers as a million rounds of measurement results are produced every second. If we don’t decode fast enough, we encounter an exponentially growing backlog of syndrome data. For useful quantum computing, we need to push the scale of the decoder up to so-called Teraquop decoding speeds.   

We are proud to partner with world-leading hardware partners and academic labs to deeply understand the quantum stack at all levels, from the qubits up

Frequently asked questions

What is the difference between quantum error correction and quantum error mitigation?

Quantum error correction (QEC) and quantum error mitigation (QEM) are two different schemes to deal with noise in devices, which can cause errors in computation.

Quantum error correction methods use multiple physical qubits to represent a single logical qubit. Data is preserved by distributing the information across multiple qubits. Quantum decoders can then detect and correct any errors that occur during computation. Surface code is a popular QEC code.

By contrast, quantum error mitigation methods are employed to infer less noisy outcomes of quantum computations, rather than correcting them. This is often done by repeatedly running slightly different circuits and classically post-processing the results. As an example, zero noise extrapolation is a popular error mitigation method.

QEM methods provide a reduction in noise that can be useful in the NISQ (noisy intermediate-scale quantum) era, as restraints in quantum hardware can make full quantum error correction less feasible. However, for useful computation involving many qubits and deep circuits, full quantum error correction will be necessary.

What is the difference between error corrected and fault tolerant quantum computers?

Quantum error correction and fault-tolerant quantum computers are often informally used interchangeably. To experts the terms have slightly difference meanings.

Quantum error correction is a scheme for protecting information from noise in device.

Fault-tolerance builds on this. Fault-tolerant quantum computers also prevent errors from spreading during the error correction process or during a computation. It is a richer and broader subject.

To build a useful quantum computer, we really do need fault-tolerance and not just error correction. At Riverlane, we are really solving the fault-tolerance problem, but often just call out “quantum error correction” since this phrase is more commonly known by non-experts.