Loading...
Organizing Committee
Virginia Tech
Virginia Tech
The University of Arizona
The University of Arizona
Abstract
Fault tolerance is essential for reliable quantum computation because quantum information (qubits) is inherently fragile. This workshop gathers experts on two primary, interconnected thrusts to advance fault-tolerant quantum computing: quantum low-density parity-check (qLDPC) codes and the Clifford hierarchy. Several families of qLDPC codes have been constructed recently, including quantum Tanner, hypergraph product, and lifted product codes. While they perform well when paired with iterative decoders, their capabilities remain to be fully understood. In particular, it remains an open question how to employ these constructions to achieve provably strong performance in practical (finite-length) settings and to describe decoding failures. Another key challenge is to leverage the Clifford hierarchy, the first two levels of which are the Pauli group and Clifford group, respectively. Because a classical computer can efficiently simulate the Clifford group, additional gates are needed for quantum computation. There are synergies across these thrusts, especially the theory of qLDPC codes that respect gates that support fault-tolerant quantum computing.
Loading...
Loading participant list in background...
Workshop Schedule
Saturday, April 11, 2026
9:00 - 9:30 AM EDT
Check In
11th Floor Collaborative Space
9:30 - 9:40 AM EDT
Welcome
11th Floor Lecture Hall
Brendan Hassett, ICERM/Brown University
9:40 - 10:25 AM EDT
Quantum Computing and Cellular Phones
11th Floor Lecture Hall
Speaker
Robert Calderbank, Duke University
Session Chair
Hiram López, Virginia Tech
Abstract
This talk will describe how the geometry of the Heisenberg-Weyl group connects the world of quantum computing and the world of wireless communication. In quantum computing the Heisenberg-Weyl group appears as the Pauli group, generated by bit shifts and phase shifts. In wireless communication the Heisenberg-Weyl group is generated by shifts in delay and Doppler. In quantum computing, the geometry of commutative subgroups is used to construct quantum error-correcting codes. In wireless communication, this geometry is used to construct low-complexity signal processing algorithms that might find application in 6G wireless systems.
10:35 - 11:05 AM EDT
Coffee Break
11th Floor Collaborative Space
11:05 - 11:50 AM EDT
Quantum Lego Power-up: Designing Transversal Gates with Tensor Networks
11th Floor Lecture Hall
Speaker
Charles Cao, Virginia Tech
Session Chair
Hiram López, Virginia Tech
Abstract
Transversal gates are the simplest form of fault-tolerant gates and are relatively easy to implement in practice. Yet designing codes that support useful transversal operations---especially non-Clifford or addressable gates---remains difficult within the stabilizer formalism or CSS constructions alone. We show that these limitations can be overcome using tensor-network frameworks such as the quantum lego formalism, where transversal gates naturally appear as global or localized symmetries. Within the quantum lego formalism, small codes carrying desirable symmetries can be "glued" into larger ones, with operator-flow rules guiding how logical symmetries are preserved. This approach enables the systematic construction of codes with addressable transversal single- and multi-qubit gates targeting specific logical qubits regardless of whether the gate is Clifford or not. As a proof of principle, we build new finite-rate code families that support strongly transversal T, CCZ, SH, and Gottesman's K3 gates---structures that are challenging to realize with conventional methods. We further construct holographic and fractal-like codes that admit addressable transversal inter-, meso-, and intra-block T, CS, and multi-control Z gates.
12:00 - 12:05 PM EDT
Group Photo (Immediately After Talk)
11th Floor Lecture Hall
12:05 - 2:00 PM EDT
Lunch/Free Time
2:00 - 2:45 PM EDT
Codes in the simplex and their use in quantum
11th Floor Lecture Hall
Speaker
Alexander Barg, University of Maryland
Session Chair
Gretchen Matthews, Virginia Tech
Abstract
Classical codes in the discrete simplex find uses in controlling error correction in quantum channels with photon losses. A study into asymptotic parameters of these codes reveals interesting features arising in the asymptotic regime, related to the typical properties of vectors in the simplex. We present several existence theorems for this class of codes and discuss their implications for quantum error correction. Based on joint works with Arda Aydin and Dor Elimelech.
2:55 - 3:15 PM EDT
Coffee Break
11th Floor Collaborative Space
3:15 - 4:00 PM EDT
New Frontiers in Continuous Variables
11th Floor Lecture Hall
Virtual Speaker
Victor Albert, National Institute of Standartds and Technology
Session Chair
Gretchen Matthews, Virginia Tech
Abstract
Continuous-variable (CV) quantum systems underpin free-space and fiber-optic communication links as well as photonic and phononic platforms for computation and simulation. Like all quantum systems, CV systems require error correction to counteract noise, yet CV quantum error correction remains relatively underexplored because conventional discrete-variable coding theory offers limited guidance. I present several new classes of CV error-correcting codes and associated fault-tolerant gadgets that extend beyond discrete-variable approaches by exploiting both the energy per mode (“depth”) and the number of modes (“breadth”) of the system’s Hilbert space.
4:15 - 5:00 PM EDT
Limits on Transversal and Fold-Transversal Gates
11th Floor Lecture Hall
Speaker
Daniel Gottesman, University of Maryland
Session Chair
Gretchen Matthews, Virginia Tech
Abstract
High-rate codes are very attractive for quantum fault tolerance because of their low qubit overhead. Performing gates on code blocks containing multiple logical qubits presents particular challenges. In some cases, however, because the logical qubits are delocalized compared to the physical qubits, even transversal gates can perform multiple-qubit logical gates. However, we prove that there are definite limits to this approach. We show that transversal Clifford gates or code automorphisms (transversal gates plus permutations of qubits) can never achieve the full 2-qubit logical Clifford group, and fold-transversal Clifford gates cannot achieve the full 3-qubit logical Clifford group.
This is work with Aranya Chakraborty, arXiv:2602.13395 [quant-ph].
5:15 - 6:30 PM EDT
Reception
11th Floor Collaborative Space
Sunday, April 12, 2026
9:00 - 9:45 AM EDT
Trivariate Tricycle Codes
11th Floor Lecture Hall
Speaker
Dan Browne, University College London
Session Chair
Narayanan Rengaswamy, The University of Arizona
Abstract
While quantum low-density parity check (qLDPC) codes are a low-overhead means of quantum information storage, it is valuable for quantum codes to possess fault-tolerant features beyond this resource efficiency. Recently, we introduced trivariate tricycle (TT) codes [1]. TT codes are a natural generalisation of the bivariate bicycle codes. They are a family of CSS codes based on a length-3 chain complex, and are defined from three trivariate polynomials, with the 3D toric code (3DTC) belonging to this construction.
In my talk I will focus on the rich set of fault tolerant gates these codes support, including a large set of transversal Clifford gates and automorphisms within and between code blocks, and (for several sub-constructions) constant-depth implementations of a (non-Clifford) gate.
[1] A. Jacob, C. McLauchlan, D. E. Browne, arXiv:2508.08191 [quant-ph] (2025)
9:55 - 10:15 AM EDT
Coffee Break
11th Floor Collaborative Space
10:15 - 11:00 AM EDT
Fail fast: techniques to probe rare events in quantum error correction
11th Floor Lecture Hall
Speaker
Theodore Yoder, IBM Quantum
Session Chair
Narayanan Rengaswamy, The University of Arizona
Abstract
The ultimate goal of quantum error correction is to create logical qubits with very low error rates (e.g. 1e-12) and assemble them into large-scale quantum computers capable of performing many (e.g. billions) of logical gates on many (e.g. thousands) of logical qubits. However, it is necessarily difficult to directly assess the performance of such high-quality logical qubits using standard Monte Carlo sampling because logical failure events become very rare. Building on existing approaches to this problem, we develop three complementary techniques to characterize the rare-event regime for general quantum low-density parity-check (qLDPC) codes under circuit noise. (I) We propose a well-motivated, low-parameter ansatz for the failure spectrum (the fraction of fault sets of each size that fail) that empirically fits all the QEC systems we studied and predicts logical error rates at all physical error rates. (II) We find min-weight logical operators of syndrome measurement circuits and exactly compute the number of min-weight failing configurations. (III) We generalize the splitting method to qLDPC codes using multi-seeded Metropolis sampling to improve convergence for systems with many inequivalent logical operators. We apply these tools to distance-6, -12, and -18 bivariate bicycle codes under circuit noise, observing strong low-error-rate performance with the recently proposed Relay decoder but also considerable scope for further improvement.
11:15 AM - 12:00 PM EDT
Qudit Lifted Product Codes with Good Parameters
11th Floor Lecture Hall
Virtual Speaker
Lalitha Vadlamani, Internation Instititute of Information Technology Hyderabad
Session Chair
Narayanan Rengaswamy, The University of Arizona
Abstract
Quantum low-density parity-check (QLDPC) codes are a promising approach to achieving fault-tolerant quantum computation with low space and time overhead. While asymptotically good qubit QLDPC codes have recently been constructed via the lifted product (LP) method, the existence of analogous codes for higher dimensional qudits remained an open question, particularly for non-prime qudit dimensions. In this work, we resolve this question affirmatively by introducing a qudit generalization of the LP construction, which extends hypergraph product and lifted product codes to arbitrary qudit dimensions. We provide a detailed analysis of qudit LP codes and explore their connection to additive quantum codes to establish bounds on encoding rates. We further demonstrate that, under appropriate constraints, qudit lifted product codes form asymptotically good families with sublinear scaling of both the number of logical qudits and the minimum distance. In addition, we study decoding strategies for qudit QLDPC codes, comparing an additive decoder suitable for general qudit codes and a linear decoder optimized for fully stacked constructions. Monte Carlo simulations show that qudit codes outperform comparable qubit codes in logical error rates and that the linear decoder provides further performance gains for fully stacked codes.
12:00 - 2:00 PM EDT
Lunch/Free Time/Departure
Lunch/Free Time
Application Information
The deadline to submit an application to this program has passed.
Your Visit to ICERM
- ICERM Facilities
- ICERM is located on the 10th & 11th floors of 121 South Main Street in Providence, Rhode Island. ICERM's business hours are 8:30am - 5:00pm during this event. See our facilities page for more info.
- Traveling to ICERM
- ICERM is located at Brown University in Providence, Rhode Island. Providence's T.F. Green Airport (15 minutes south) and Boston's Logan Airport (1 hour north) are the closest airports. Providence is also on Amtrak's Northeast Corridor. See our travel page for full directions.
- Lodging
- Confirmed participants will receive an email to book a room at our preferred hotel, the Hampton Inn & Suites Providence Downtown. Contact programstaff@icerm.brown.edu with questions.Only use hotel links from ICERM’s official emails or this page. ICERM never uses third-party booking vendors.
- Childcare/Schools
- Those traveling with family can contact housing@icerm.brown.edu for childcare and school information.
- Technology Resources
- Wireless internet access and wireless printing are available for all ICERM visitors. Eduroam is supported. Thin clients provide access to web browsers, SSH terminals, and printing. See our Technology Resources page for setup info.
- Accessibility
- For special services, accommodations, or assistance, please contact accessibility@icerm.brown.edu in advance. Thank you.
- Discrimination and Harassment Policy
- ICERM is committed to a safe, professional, and welcoming environment. Brown University's Code of Conduct and related policies apply to all ICERM participants. Contact the ICERM Director or Associate Director Jenna Sousa for concerns.
- Fundamental Research
- ICERM programs promote Fundamental Research and mathematical education. Participants involved in sensitive or proprietary work should be aware of U.S. export control restrictions.
- Exploring Providence
- Providence offers world-class dining and attractions. Visit our Explore Providence page to see what’s near ICERM.
Visa Information
Contact visa@icerm.brown.edu for assistance.
- Eligible to be reimbursed
- B-1 or Visa Waiver Business (WB)
- Ineligible to be reimbursed
- B-2 or Visa Waiver Tourist (WT)
- Already in the US?
F-1 and J-1 not sponsored by ICERM: need to obtain a letter approving reimbursement from the International Office of your home institution prior to travel.
H-1B holders do not need a letter of approval.
All other visas: alert ICERM staff immediately about your situation.
ICERM does not reimburse visa fees. This chart is to inform visitors whether the visa they enter the US on allows them to receive reimbursement for the items outlined in their invitation letter.
Financial Support
This section is for general purposes only and does not indicate that all attendees receive funding. Please refer to your personalized invitation to review your offer.
- ORCID iD
- As this program is funded by the National Science Foundation (NSF), ICERM is required to collect your ORCID iD if you are receiving funding to attend this program. Be sure to add your ORCID iD to your Cube profile as soon as possible to avoid delaying your reimbursement.
- Acceptable Costs
- 1 roundtrip between your home institute and ICERM
- Flights in economy class to either Providence airport (PVD) or Boston airport (BOS)
- Ground Transportation to and from airports and ICERM.
- Unacceptable Costs
- Flights on U.K. airlines
- Seats in economy plus, business class, or first class
- Change ticket fees of any kind
- Multi-use bus passes
- Meals or incidentals
- Advance Approval Required
- Personal car travel to ICERM from outside New England
- Multiple-destination plane ticket; does not include layovers to reach ICERM
- Arriving or departing from ICERM more than a day before or day after the program
- Multiple trips to ICERM
- Rental car to/from ICERM
- Arriving or departing from airport other than PVD/BOS or home institution’s local airport
- 2 one-way plane tickets to create a roundtrip (often purchased from Expedia, Orbitz, etc.)
- Travel Maximum Contributions
- New England: $350
- Other contiguous US: $850
- Asia & Oceania: $2,000
- All other locations: $1,500
- Note these rates were updated in Spring 2023 and supersede any prior invitation rates.
- Reimbursement Requests
Request Reimbursement with Cube
Refer to the back of your ID badge for more information. Checklists are available at the front desk and in the Reimbursement section of Cube.
- Reimbursement Tips
- Scanned original receipts are required for all expenses
- Airfare receipt must show full itinerary and payment
- ICERM does not offer per diem or meal reimbursement
- Allowable mileage is reimbursed at prevailing IRS Business Rate and trip documented via Google Maps PDF
- Keep all documentation until you receive your reimbursement!
- Reimbursement Timing
6–8 weeks after all documentation is sent to ICERM. All reimbursements are reviewed by multiple Brown University offices.
- Reimbursement Deadline
Submissions must be received within 30 days of ICERM departure to avoid applicable taxes. No submissions are accepted after six months.