The critical caveat is that quantum algorithms require

The gap

Evidence profile

Stated in the cells research gap and future work and cells limitations and cells future research and discussion and inline gaps sections of the source papers, classified as general, drawn from work published between 2024 and 2026, spanning 5 journals. Those papers have been cited 616 times in total.

Supporting evidence — 7 representative gaps

• Simple logical quantum computation with concatenated symplectic double codes (2026) · Quantum · doi

  The paper identifies a gap in the study of performing fault-tolerant logical gates on quantum error correcting codes. - There is a need for more efficient and scalable codes. - The authors note that concatenated symplectic double codes have not been fully explored.

  generalstated in cells research gap
  Keywords: paper identifies gap study performing fault-tolerant logical gates
• Quantum error correction below the surface code threshold (2024) · Nature · cited 616× · doi

  In this work, we have demonstrated surface code memory below the threshold in our new Willow architecture. Each time the code distance increases by two, the logical error per cycle is reduced by more than half, culminating in a distance-7 logical lifetime of more than double its best constituent physical qubit lifetime. This signature of exponential logical error suppression with code distance forms the foundation of running large-scale quantum algorithms with error correction. Our error-corrected processors also demonstrate other key advances towards fault-tolerant quantum computing. We achieve repeatable performance for more than several hours and run experiments up to 106 cycles without deteriorating performance, both of which are necessary for future large-scale fault-tolerant algorithms. Furthermore, we have ArticleabcdProcessingGraph bufferCompletePastBlossomFuseFuseTaskgraphNowNot started0012345FutureShot latencySubshot latency0, 12, 31, 23, 44, 5RTNumber of cyclesNNEns.12345..., 05, ...10–210–3Logical errorper cycle, d30010030103104105106Latency (μs)d = 3d = 5engineered a real-time decoding system with only a modest reduction in accuracy compared with our offline decoders. Even so, many challenges remain ahead of us. Although we might, in principle, achieve low logical error rates by scaling up our current processors, it would be resource intensive in practice. Extrapolating the projections shown in Fig. 1d, achieving a 10−6 error rate would require a distance-27 logical qubit using 1,457 physical qubits. Scaling up will bring additional challenges in real-time decoding as the syndrome measurements per cycle increase quadratically with the code distance. Our repetition code experiments also identify a noise floor at an error rate of 10−10 caused by correlated bursts of errors. Identifying and miti- gating this error mechanism will be integral to running larger quantum algorithms. However, quantum error correction also provides us exponential leverage in reducing logical errors with processor improvements. For example, reducing physical error rates by a factor of two would improve the distance-27 logical performance by four orders of magnitude, well into algorithmically relevant error rates11,12. We further expect these overheads to reduce with advances in error correction protocols47–53 and decoding54–56. The purpose of quantum error correction is to enable large-scale quantum algorithms. Although this work focuses on building a robust memory, additional challenges will arise in logical computation57,58. On the classical side, we must ensure that software elements including our calibration protocols, real-time decoders and logical compilers can scale to the sizes and complexities needed to run multiple sur- face code operations59. With below-threshold surface codes, we have demonstrated processor performance that can scale in principle, but which we must now scale in practice.

  generalstated in future workevidence 5/5
  Keywords: error logical code distance scale quantum time algorithms correction performance cycle physical large real decoding
• Hoare meets Heisenberg: A Lightweight Logic for Quantum Programs (2026) · Quantum · doi

  There are still various ways to further enrich our program logic, providing many promising avenues for us to explore. Inference on Quantum Channels Other than measurement, all the operations whose behavior we infer are unitary circuits. More general quantum operations are given by completely positive trace-preserving maps, i.e., quantum channels. Extending our logic to handle quantum channels could potentially allow us to perform inference on or validate quantum cryptography and communication protocols. A starting point for this would be to use additive predicates and disjunctions to characterize partial traces and post-selection. Implementing a fault-tolerant universal set Applications for error-correcting codes of gates transversally will reduce the overall cost of error correction. However, as this cannot be achieved using just one code, a common method used switches between two sets of codes, each having a different set of transversal gates [2]. Extending our logic to either infer the structure of or even validate the code-switching circuit given the predicates describing two codes would prove to be fruitful. Similarly, validating the encoding and decoding circuits for a code given its predicate could also be of value in verifying the implementation of error-correcting codes. Normalization for additive predicates Finding a canonical representation for additive predicates is imperative to effectively validate additive postconditions. A big roadblock to it is that, unlike with Pauli predicates, additive predicates (especially multi-qubit ones) could have terms that neither commute nor anticommute. This makes it hard to find a normalization procedure for them similar to that in §3. Additionally, this also limits our ability to make multi-qubit separability judgments in the additive case. Backwards reasoning In Remark 21 we noted that our logic can be used for backwards, as well as forwards, reasoning about quantum circuits. Right now, this is limited to unitary gates, since measurement isn’t reversible in the way unitary operations are. We could flesh out the logic to support backwards reasoning with measurement in the style of [37] and others. General measurement for additive predicates Although we have outlined some cases in §9 where we can infer the post-measurement states, this is limited to performing z-basis measurement on single and two-qubit systems. In order to fully exploit the power of additive predicates, it is essential that we have a full characterization for post-measurement states. An immediate consequence of this could be a deeper analysis of predicates for multi- qubit magic states and applications associated with them. Accepted in Quantum 2026-06-26, click title to verify. Published under CC-BY 4.0. 50 A logic for quantum programs with classical control A key component of quan- tum error correction and many quantum algorithms in practice (whether intermediate or large scale) is that they are interspersed with classical processing. This includes the use of classical control to decide which quantum operations to apply along with any pre- or post-processing. To account for this, we would need to formally extend our logic to ex- plicitly handle classical data types as well as other program elements such as conditional statements, loops, and recursion. This would involve extending both the language and the program logic itself, in the vein of the classical-quantum states of Feng and Ying [10] and Ying [36] and their associated logics.

  generalstated in future workevidence 5/5
  Keywords: quantum predicates logic additive measurement classical operations post error codes qubit states program channels infer
• A Comparative Analysis of Classical and Quantum Algorithms through the Environmental Impact Lens (2026) · International Journal For Multidisciplinary Research · doi

  The critical caveat is that quantum algorithms require quantum hardware. - The paper acknowledges that fault-tolerant operation remains the primary near-term milestone for quantum computing.

  generalstated in cells limitationsevidence 5/5
  Keywords: critical caveat quantum algorithms require hardware paper acknowledges
• A Forward (epsilon, omega) Calculus for Quantum Readout Error and the Classical Post-Processing of Measurement Outcomes (2026) · Zenodo (CERN European Organization for Nuclear Research) · doi

  To apply the proposed calculus to more complex quantum error correction techniques, such as surface codes and concatenated codes. - To investigate the effectiveness of the proposed method in handling other types of errors, such as coherent errors and leakage errors. - To optimize the proposed calculus for practical implementation in quantum processors.

  generalstated in cells future researchevidence 5/5
  Keywords: apply proposed calculus complex quantum error correction techniques
• Verifier-initiated quantum message-authentication via quantum zero-knowledge proofs (2026) · Nature Communications · doi

  Future work will investigate error-tolerant variants, potentially using quantum error correction or fault-tolerant techniques to maintain security under realistic conditions. One limitation of our current protocol is its assumption of noise- free quantum systems and perfect quantum gates.

  generalstated in discussionevidence 4/5
  Keywords: quantum error tolerant future investigate variants potentially using correction fault techniques maintain security realistic conditions
• Simple logical quantum computation with concatenated symplectic double codes (2026) · Quantum · doi

  We hypothesized that these codes have convenient non-Clifford gates facilitated through zero-level distillation of the logical |CZ⟩ state; however, further work is required to determine whether this method is viable in general. There are several open questions to be answered and improvements to be made be- fore C4-CSD codes solidify themselves as a leading contender for fault-tolerant quantum computation: 1.

  generalstated in inline gapsevidence 3/5
  Keywords: codes hypothesized convenient clifford gates facilitated zero level distillation logical state further required determine whether

Questions about this gap