# Holographic code[1]

## Description

A code whose encoding isometry serves to model aspects of the AdS/CFT holographic duality. Encoding map models radial time evolution for a fixed time slice in Anti de Sitter (AdS) space, mapping operators in the bulk of AdS, represented by logical qudits, onto operators on the boundary of the corresponding Conformal Field Theory (CFT), represented by physical qudits. Encoding can often be represented by a tensor network associated with a tiling of hyperbolic space. See Defn 4.3 of Ref. [2] for a technical formulation.

Typically, the encoding isometry \(U\) obeys the entanglement-wedge reconstruction condition, which states that for any boundary region \(R\), any bulk operator \(O\) localized to the entanglement wedge of \(R\) must be implementable by some boundary operator \(\tilde{O}\) localized to \(R\). Formally, \(UO = \tilde{O}U\) and \([\tilde{O},UU^\dagger] = 0\). The entanglement wedge is the space enclosed within the Ryu–Takayanagi surface in the bulk (minimal surface) with boundary \(R\).

## Protection

## Transversal Gates

## Code Capacity Threshold

## Notes

## Parent

## Children

- Pastawski-Yoshida-Harlow-Preskill (HaPPY) code
- Three qutrit code — Three-qutrit code is a minimal model for holography [3][8].

## Cousins

- Operator-algebra error-correcting code — Properties of holographic codes are often quantified in the Heisenberg picture, i.e., in terms of operator algebras [3][4].
- Hyperbolic surface code — Both holographic and hyperbolic surface codes utilize tesselations of hyperbolic surfaces. Encodings for the former are hyperbolically tiled tensor networks, while the latter is defined on hyperbolically tiled physical-qubit lattices.
- Matrix-model code — Matrix-model codes are motivated by the Ads/CFT correspondence because it is manifest in continuous non-Abelian gauge theories with large gauge groups [9].
- Quantum Lego code — Holographic codes whose encoders are tensor networks discretizing hyperbolic space are quantum Lego codes.
- Renormalization group (RG) cat code — The RG cat code encoder has similar coarse-graining features as that of a holographic code [10].

## References

- [1]
- F. Pastawski et al., “Holographic quantum error-correcting codes: toy models for the bulk/boundary correspondence”, Journal of High Energy Physics 2015, (2015). DOI; 1503.06237
- [2]
- K. Dolev et al., “Gauging the bulk: generalized gauging maps and holographic codes”, Journal of High Energy Physics 2022, (2022). DOI; 2108.11402
- [3]
- A. Almheiri, X. Dong, and D. Harlow, “Bulk locality and quantum error correction in AdS/CFT”, Journal of High Energy Physics 2015, (2015). DOI; 1411.7041
- [4]
- F. Pastawski and J. Preskill, “Code Properties from Holographic Geometries”, Physical Review X 7, (2017). DOI; 1612.00017
- [5]
- S. Cree et al., “Fault-Tolerant Logical Gates in Holographic Stabilizer Codes Are Severely Restricted”, PRX Quantum 2, (2021). DOI; 2103.13404
- [6]
- N. Bao, C. Cao, and G. Zhu, “Deconfinement and error thresholds in holography”, Physical Review D 106, (2022). DOI; 2202.04710
- [7]
- Daniel Harlow and Hirosi Ooguri, “Symmetries in quantum field theory and quantum gravity”. 1810.05338
- [8]
- D. Harlow, “The Ryu–Takayanagi Formula from Quantum Error Correction”, Communications in Mathematical Physics 354, 865 (2017). DOI; 1607.03901
- [9]
- ChunJun Cao, Gong Cheng, and Brian Swingle, “Large $N$ Matrix Quantum Mechanics as a Quantum Memory”. 2211.08448
- [10]
- K. Furuya, N. Lashkari, and S. Ouseph, “Real-space RG, error correction and Petz map”, Journal of High Energy Physics 2022, (2022). DOI; 2012.14001

## Page edit log

- Victor V. Albert (2022-03-08) — most recent
- Joel Rajakumar (2021-12-20)

## Zoo code information

## Cite as:

“Holographic code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2023. https://errorcorrectionzoo.org/c/holographic

Github: https://github.com/errorcorrectionzoo/eczoo_data/tree/main/codes/quantum/properties/holographic.yml.