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1. Demonstrating multi-round subsystem quantum error correction using matching and maximum likelihood decoders

Author

Neereja Sundaresan, Theodore J. Yoder, Youngseok Kim, Muyuan Li, Edward H. Chen, Grace Harper, Ted Thorbeck, Andrew W. Cross, Antonio D. Córcoles, and Maika Takita

Subjects
Science
Abstract

Abstract Quantum error correction offers a promising path for performing high fidelity quantum computations. Although fully fault-tolerant executions of algorithms remain unrealized, recent improvements in control electronics and quantum hardware enable increasingly advanced demonstrations of the necessary operations for error correction. Here, we perform quantum error correction on superconducting qubits connected in a heavy-hexagon lattice. We encode a logical qubit with distance three and perform several rounds of fault-tolerant syndrome measurements that allow for the correction of any single fault in the circuitry. Using real-time feedback, we reset syndrome and flag qubits conditionally after each syndrome extraction cycle. We report decoder dependent logical error, with average logical error per syndrome measurement in Z(X)-basis of ~0.040 (~0.088) and ~0.037 (~0.087) for matching and maximum likelihood decoders, respectively, on leakage post-selected data.

Published
2023
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2. Implementing stakeholder engagement to explore alternative models of consent: An example from the PREP-IT trials

Author

Guillermo Pechero, Jr., MD, Branden Pfaff, Mayank Rao, David Pogorzelski, Paula McKay, Ella Spicer, Andrea Howe, Haley K. Demyanovich, Debra L. Sietsema, Michael F. McTague, Lolita Ramsey, Martha Holden, Joshua Rudnicki, Jeff Wells, Michelle Medeiros, Gerard P. Slobogean, Sheila Sprague, Jeffrey Wells, Mohit Bhandari, Robert V. O'Toole, Jean-Claude D'Alleyrand, Andrew Eglseder, Aaron Johnson, Christopher Langhammer, Christopher Lebrun, Theodore Manson, Jason Nascone, Ebrahim Paryavi, Raymond Pensy, Andrew Pollak, Marcus Sciadini, Yasmin Degani, Nathan N. O'Hara, Katherine Joseph, Megan Camara, Anthony D. Harris, Daniel C. Mullins, Lehana Thabane, Amber Wood, Gregory J. Della Rocca, Joan Hebden, Kyle J. Jeray, Lucas Marchand, Lyndsay M. O'Hara, Robert Zura, Michael J. Gardner, Jenna Blasman, Jonah Davies, Stephen Liang, Monica Taljaard, P.J. Devereaux, Gordon H. Guyatt, Diane Heels-Ansdell, Debra Marvel, Jana Palmer, Jeff Friedrich, Ms Frances Grissom, I. Leah Gitajn, Saam Morshed, Bradley A. Petrisor, Franca Mossuto, Manjari G. Joshi, Justin Fowler, Jessica Rivera, Max Talbot, Shannon Dodds, Alisha Garibaldi, Silvia Li, Uyen Nguyen, Alejandra Rojas, Taryn Scott, Gina Del Fabbro, Olivia Paige Szasz, Haley Demyanovich, Kelly Little, C. Daniel Mullins, Eric Kettering, Diamond Hale, Brad A. Petrisor, Herman Johal, Bill Ristevski, Dale Williams, Matthew Denkers, Krishan Rajaratnam, Jamal Al-Asiri, Jordan Leonard, Francesc A. Marcano-Fernández, Jodi Gallant, Federico Persico, Marko Gjorgjievski, Annie George, Roman M. Natoli, Greg E. Gaski, Todd O. McKinley, Walter W. Virkus, Anthony T. Sorkin, Jan P. Szatkowski, Joseph R. Baele, Brian H. Mullis, Lauren C. Hill, Andrea Hudgins, Patrick Osborn, Sarah Pierrie, Eric Martinez, Joseph Kimmel, John D. Adams, Michael L. Beckish, Christopher C. Bray, Timothy R. Brown, Andrew W. Cross, Timothy Dew, Gregory K. Faucher, Richard W. Gurich, Jr., David E. Lazarus, S. John Millon, M. Jason Palmer, Scott E. Porter, Thomas M. Schaller, Michael S. Sridhar, John L. Sanders, L. Edwin Rudisill, Jr., Michael J. Garitty, Andrew S. Poole, Michael L. Sims, Clark M. Walker, Robert M. Carlisle, II, Erin Adams Hofer, Brandon S. Huggins, Michael D. Hunter, William A. Marshall, Shea Bielby Ray, Cory D. Smith, Kyle M. Altman, Julia C. Bedard, Markus F. Loeffler, Erin R. Pichiotino, Austin A. Cole, Ethan J. Maltz, Wesley Parker, T. Bennett Ramsey, Alex Burnikel, Michael Colello, Russell Stewart, Jeremy Wise, M. Christian Moody, Stephanie L. Tanner, Rebecca G. Snider, Christine E. Townsend, Kayla H. Pham, Abigail Martin, Emily Robertson, Theodore Miclau, Utku Kandemir, Meir Marmor, Amir Matityahu, R. Trigg McClellan, Eric Meinberg, David Shearer, Paul Toogood, Anthony Ding, Erin Donohoe, Jothi Murali, Tigist Belaye, Eleni Berhaneselase, Alexandra Paul, Kartik Garg, Joshua L. Gary, Stephen J. Warner, John W. Munz, Andrew M. Choo, Timothy S. Achor, Milton L. “Chip” Routt, Guillermo Pechero, Adam Miller, Jennifer E. Hagen, Matthew Patrick, Richard Vlasak, Thomas Krupko, Kalia Sadasivan, Chris Koenig, Daniel Bailey, Daniel Wentworth, Chi Van, Justin Schwartz, Niloofar Dehghan, Clifford B. Jones, J. Tracy Watson, Michael McKee, Ammar Karim, Michael Talerico, Alyse Williams, Tayler Dykes, William T. Obremskey, Amir Alex Jahangir, Manish Sethi, Robert Boyce, Daniel J. Stinner, Phillip Mitchell, Karen Trochez, Andres Rodriguez, Vamshi Gajari, Elsa Rodriguez, Charles Pritchett, Christina Boulton, Jason Lowe, Jason Wild, John T. Ruth, Michel Taylor, Andrea Seach, Sabina Saeed, Hunter Culbert, Alejandro Cruz, Thomas Knapp, Colin Hurkett, Maya Lowney, Michael Prayson, Indresh Venkatarayappa, Brandon Horne, Jennifer Jerele, Linda Clark, Francesc Marcano-Fernández, Montsant Jornet-Gibert, Laia Martínez-Carreres, David Martí-Garín, Jorge Serrano-Sanz, Joel Sánchez-Fernández, Matsuyama Sanz-Molero, Alejandro Carballo, Xavier Pelfort, Francesc Acerboni-Flores, Anna Alavedra-Massana, Neus Anglada-Torres, Alexandre Berenguer, Jaume Cámara-Cabrera, Ariadna Caparros-García, Ferran Fillat-Gomà, Ruben Fuentes-López, Ramona Garcia-Rodriguez, Nuria Gimeno-Calavia, Guillem Graells-Alonso, Marta Martínez-Álvarez, Patricia Martínez-Grau, Raúl Pellejero-García, Ona Ràfols-Perramon, Juan Manuel Peñalver, Mònica Salomó Domènech, Albert Soler-Cano, Aldo Velasco-Barrera, Christian Yela-Verdú, Mercedes Bueno-Ruiz, Estrella Sánchez-Palomino, Ernesto Guerra-Farfan, Jordi Tomas-Hernandez, Jordi Teixidor-Serra, Vicente Molero-Garcia, Jordi Selga-Marsa, Juan Antonio Porcel-Vasquez, Jose Vicente Andres-Peiro, Joan Minguell-Monyart, Yaiza Garcia-Sanchez, Jorge Nuñez-Camarena, Eladia Tauste-Rubio, Marta Gonzalez-Amigo, Nicholas M. Romeo, Heather A. Vallier, Mary A. Breslin, Joanne Fraifogl, Eleanor S. Wilson, Leanne K. Wadenpfuhl, Paul G. Halliday, Darius G. Viskontas, Kelly L. Apostle, Dory S. Boyer, Farhad O. Moola, Bertrand H. Perey, Trevor B. Stone, H. Michael Lemke, Mauri Zomar, Chen “Brenda” Fan, Kyrsten Payne, Kevin Phelps, Michael Bosse, Madhav Karunakar, Laurence Kempton, Stephen Sims, Joseph Hsu, Rachel Seymour, Christine Churchill, Claire Bartel, Robert Miles Mayberry, Maggie Brownrigg, Cara Girardi, Ada Mayfield, Robert A. Hymes, Cary C. Schwartzbach, Jeff E. Schulman, A. Stephen Malekzadeh, Michael A. Holzman, James S. Ahn, Farhanaz Panjshiri, Sharmistha Das, Antoinisha D. English, Sharon M. Haaser, Jaslynn A.N. Cuff, Holly Pilson, Eben A. Carroll, Jason J. Halvorson, Sharon Babcock, J. Brett Goodman, Martha B. Holden, Debra Bullard, Wendy Williams, Thomas F. Higgins, Justin M. Haller, David L. Rothberg, Lucas S. Marchand, Ashley Neese, Mark Russell, Zachary M. Olsen, Marcus Coe, Kevin Dwyer, Devin S. Mullin, Clifford A. Reilly, Peter DePalo, Amy E. Hall, Marilyn Heng, Mitchel B. Harris, R. Malcolm Smith, David W. Lhowe, John G. Esposito, Mira Bansal, Patrick F. Bergin, George V. Russell, Matthew L. Graves, John Morellato, Heather K. Champion, Leslie N. Johnson, Sheketha L. McGee, Eldrin L. Bhanat, Samir Mehta, Derek Donegan, Jaimo Ahn, Annamarie Horan, Mary Dooley, Ashley Kuczinski, Ashley Iwu, David Potter, Robert VanDemark, III, Troy Hollinsworth, Michael J. Weaver, Arvind G. von Keudell, Elizabeth M. Allen, Todd Jaeblon, Robert Beer, Mark J. Gage, Rachel M. Reilly, and Cindy Sparrow

Subjects
Cluster randomized crossover, Stakeholder engagement, Consent, Deferred consent, Trial design, Patient advisors, Medicine (General), R5-920
Abstract

Introduction: Cluster randomized crossover trials are often faced with a dilemma when selecting an optimal model of consent, as the traditional model of obtaining informed consent from participant's before initiating any trial related activities may not be suitable. We describe our experience of engaging patient advisors to identify an optimal model of consent for the PREP-IT trials. This paper also examines surrogate measures of success for the selected model of consent. Methods: The PREP-IT program consists of two multi-center cluster randomized crossover trials that engaged patient advisors to determine an optimal model of consent. Patient advisors and stakeholders met regularly and reached consensus on decisions related to the trial design including the model for consent. Patient advisors provided valuable insight on how key decisions on trial design and conduct would be received by participants and the impact these decisions will have. Results: Patient advisors, together with stakeholders, reviewed the pros and cons and the requirements for the traditional model of consent, deferred consent, and waiver of consent. Collectively, they agreed upon a deferred consent model, in which patients may be approached for consent after their fracture surgery and prior to data collection. The consent rate in PREP-IT is 80.7%, and 0.67% of participants have withdrawn consent for participation. Discussion: Involvement of patient advisors in the development of an optimal model of consent has been successful. Engagement of patient advisors is recommended for other large trials where the traditional model of consent may not be optimal.

Published
2021
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3. Managing work flow in high enrolling trials: The development and implementation of a sampling strategy in the PREPARE trial

Author

David Pogorzelski, Uyen Nguyen, Paula McKay, Lehana Thabane, Megan Camara, Lolita Ramsey, Rachel Seymour, J. Brett Goodman, Sheketha McGee, Joanne Fraifogl, Andrea Hudgins, Stephanie L. Tanner, Mohit Bhandari, Gerard P. Slobogean, Sheila Sprague, Jeffrey Wells, Jean-Claude D'Alleyrand, Anthony D. Harris, Daniel C. Mullins, Amber Wood, Gregory J. Della Rocca, Joan Hebden, Kyle J. Jeray, Lucas Marchand, Lyndsay M. O'Hara, Robert Zura, Michael J. Gardner, Jenna Blasman, Jonah Davies, Stephen Liang, Monica Taljaard, P.J. Devereaux, Gordon H. Guyatt, Diane Heels-Ansdell, Debra Marvel, Jana Palmer, Jeff Friedrich, Nathan N. O'Hara, Ms. Frances Grissom, I. Leah Gitajn, Saam Morshed, Robert V. O'Toole, Bradley A. Petrisor, Franca Mossuto, Manjari G. Joshi, Justin Fowler, Jessica Rivera, Max Talbot, Shannon Dodds, Alisha Garibaldi, Silvia Li, Alejandra Rojas, Taryn Scott, Gina Del Fabbro, Olivia Paige Szasz, Andrea Howe, Joshua Rudnicki, Haley Demyanovich, Kelly Little, C. Daniel Mullins, Michelle Medeiros, Eric Kettering, Diamond Hale, Andrew Eglseder, Aaron Johnson, Christopher Langhammer, Christopher Lebrun, Theodore Manson, Jason Nascone, Ebrahim Paryavi, Raymond Pensy, Andrew Pollak, Marcus Sciadini, Yasmin Degani, Haley K. Demyanovich, Katherine Joseph, Brad A. Petrisor, Herman Johal, Bill Ristevski, Dale Williams, Matthew Denkers, Krishan Rajaratnam, Jamal Al-Asiri, Jordan Leonard, Francesc A. Marcano-Fernández, Jodi Gallant, Federico Persico, Marko Gjorgjievski, Annie George, Roman M. Natoli, Greg E. Gaski, Todd O. McKinley, Walter W. Virkus, Anthony T. Sorkin, Jan P. Szatkowski, Joseph R. Baele, Brian H. Mullis, Lauren C. Hill, Patrick Osborn, Sarah Pierrie, Eric Martinez, Joseph Kimmel, John D. Adams, Michael L. Beckish, Christopher C. Bray, Timothy R. Brown, Andrew W. Cross, Timothy Dew, Gregory K. Faucher, Richard W. Gurich, Jr., David E. Lazarus, S. John Millon, M. Jason Palmer, Scott E. Porter, Thomas M. Schaller, Michael S. Sridhar, John L. Sanders, L. Edwin Rudisill, Jr., Michael J. Garitty, Andrew S. Poole, Michael L. Sims, Clark M. Walker, Robert M. Carlisle, II, Erin Adams Hofer, Brandon S. Huggins, Michael D. Hunter, William A. Marshall, Shea Bielby Ray, Cory D. Smith, Kyle M. Altman, Julia C. Bedard, Markus F. Loeffler, Erin R. Pichiotino, Austin A. Cole, Ethan J. Maltz, Wesley Parker, T. Bennett Ramsey, Alex Burnikel, Michael Colello, Russell Stewart, Jeremy Wise, M. Christian Moody, Rebecca G. Snider, Christine E. Townsend, Kayla H. Pham, Abigail Martin, Emily Robertson, Theodore Miclau, Utku Kandemir, Meir Marmor, Amir Matityahu, R. Trigg McClellan, Eric Meinberg, David Shearer, Paul Toogood, Anthony Ding, Erin Donohue, Tigist Belaye, Eleni Berhaneselase, Alexandra Paul, Kartik Garg, Joshua L. Gary, Stephen J. Warner, John W. Munz, Andrew M. Choo, Timothy S. Achor, Milton L. “Chip” Routt, Mayank Rao, Guillermo Pechero, Adam Miller, Jennifer E. Hagen, Matthew Patrick, Richard Vlasak, Thomas Krupko, Kalia Sadasivan, Chris Koenig, Daniel Bailey, Daniel Wentworth, Chi Van, Justin Schwartz, Niloofar Dehghan, Clifford B. Jones, J Tracy Watson, Michael McKee, Ammar Karim, Michael Talerico, Debra L. Sietsema, Alyse Williams, Tayler Dykes, William T. Obremskey, Amir Alex Jahangir, Manish Sethi, Robert Boyce, Daniel J. Stinner, Phillip Mitchell, Karen Trochez, Andres Rodriguez, Vamshi Gajari, Elsa Rodriguez, Charles Pritchett, Christina Boulton, Jason Lowe, Jason Wild, John T. Ruth, Michel Taylor, Andrea Seach, Sabina Saeed, Hunter Culbert, Alejandro Cruz, Thomas Knapp, Colin Hurkett, Maya Lowney, Michael Prayson, Indresh Venkatarayappa, Brandon Horne, Jennifer Jerele, Linda Clark, Francesc Marcano-Fernández, Montsant Jornet-Gibert, Laia Martínez-Carreres, David Martí-Garín, Jorge Serrano-Sanz, Joel Sánchez-Fernández, Matsuyama Sanz-Molero, Alejandro Carballo, Xavier Pelfort, Francesc Acerboni-Flores, Anna Alavedra-Massana, Neus Anglada-Torres, Alexandre Berenguer, Jaume Cámara-Cabrera, Ariadna Caparros-García, Ferran Fillat-Gomà, Ruben Fuentes-López, Ramona Garcia-Rodriguez, Nuria Gimeno-Calavia, Guillem Graells-Alonso, Marta Martínez-Álvarez, Patricia Martínez-Grau, Raúl Pellejero-García, Ona Ràfols-Perramon, Juan Manuel Peñalver, Mònica Salomó Domènech, Albert Soler-Cano, Aldo Velasco-Barrera, Christian Yela-Verdú, Mercedes Bueno-Ruiz, Estrella Sánchez-Palomino, Ernesto Guerra, Yaiza García, Nicholas M. Romeo, Heather A. Vallier, Mary A. Breslin, Eleanor S. Wilson, Leanne K. Wadenpfuhl, Paul G. Halliday, Darius G. Viskontas, Kelly L. Apostle, Dory S. Boyer, Farhad O. Moola, Bertrand H. Perey, Trevor B. Stone, H. Michael Lemke, Mauri Zomar, Ella Spicer, Chen “Brenda” Fan, Kyrsten Payne, Kevin Phelps, Michael Bosse, Madhav Karunakar, Laurence Kempton, Stephen Sims, Joseph Hsu, Christine Churchill, Claire Bartel, Robert Miles Mayberry, Maggie Brownrigg, Cara Girardi, Ada Mayfield, Robert A. Hymes, Cary C. Schwartzbach, Jeff E. Schulman, A. Stephen Malekzadeh, Michael A. Holzman, James S. Ahn, Farhanaz Panjshiri, Sharmistha Das, Antoinisha D. English, Sharon M. Haaser, Jaslynn A.N. Cuff, Holly Pilson, Eben A. Carroll, Jason J. Halvorson, Sharon Babcock, Martha B. Holden, Debra Bullard, Wendy Williams, Thomas F. Higgins, Justin M. Haller, David L. Rothberg, Ashley Neese, Mark Russell, Marcus Coe, Kevin Dwyer, Devin S. Mullin, Clifford A. Reilly, Peter DePalo, Amy E. Hall, Marilyn Heng, Mitchel B. Harris, R. Malcolm Smith, David W. Lhowe, John G. Esposito, Mira Bansal, Patrick F. Bergin, George V. Russell, Matthew L. Graves, John Morellato, Heather K. Champion, Leslie N. Johnson, Sheketha L. McGee, Eldrin L. Bhanat, Samir Mehta, Derek Donegan, Jaimo Ahn, Annamarie Horan, Mary Dooley, Ashley Kuczinski, Ashley Iwu, David Potter, Robert VanDemark, III, Branden Pfaff, Troy Hollinsworth, Michael J. Weaver, Arvind G. von Keudell, Michael F. McTague, Elizabeth M. Allen, Todd Jaeblon, Robert Beer, Mark J. Gage, Rachel M. Reilly, and Cindy Sparrow

Subjects
Sampling, Pragmatic, Cluster crossover, Sampling framework, Work flow, Sampling strategy, Medicine (General), R5-920
Abstract

Introduction: Pragmatic trials in comparative effectiveness research assess the effects of different treatment, therapeutic, or healthcare options in clinical practice. They are characterized by broad eligibility criteria and large sample sizes, which can lead to an unmanageable number of participants, increasing the risk of bias and affecting the integrity of the trial. We describe the development of a sampling strategy tool and its use in the PREPARE trial to circumvent the challenge of unmanageable work flow. Methods: Given the broad eligibility criteria and high fracture volume at participating clinical sites in the PREPARE trial, a pragmatic sampling strategy was needed. Using data from PREPARE, descriptive statistics were used to describe the use of the sampling strategy across clinical sites. A Chi-square test was performed to explore whether use of the sampling strategy was associated with a reduction in the number of missed eligible patients. Results: 7 of 20 clinical sites (35%) elected to adopt a sampling strategy. There were 1539 patients excluded due to the use of the sampling strategy, which represents 30% of all excluded patients and 20% of all patients screened for participation. Use of the sampling strategy was associated with lower odds of missed eligible patients (297/4545 (6.5%) versus 341/3200 (10.7%) p

Published
2021
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4. Demonstration of quantum advantage in machine learning

Author

Diego Ristè, Marcus P. da Silva, Colm A. Ryan, Andrew W. Cross, Antonio D. Córcoles, John A. Smolin, Jay M. Gambetta, Jerry M. Chow, and Blake R. Johnson

Subjects
Physics, QC1-999, Electronic computers. Computer science, QA75.5-76.95
Abstract

Large advantage in small quantum computers Quantum computing promises to revolutionize all fields of science by solving problems that are too complex for conventional computers. However, the realization of a full-fledged, universal quantum computer is still far ahead, requiring millions of quantum bits and very low error rates. Despite this, D. Ristè and colleagues at Raytheon BBN Technologies, with collaborators at IBM, have demonstrated that a quantum advantage already appears with only a few quantum bits and a highly noisy system. The team solved a particular problem, known as learning parity with noise, using a five-qubit superconducting quantum processor. Counting the number of times that the processor runs, they demonstrate that the implemented quantum algorithm finds the solution much faster than by classical methods

Published
2017
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5. Experimental implementation of non-Clifford interleaved randomized benchmarking with a controlled-S gate

Author

Shelly Garion, Naoki Kanazawa, Haggai Landa, David C. McKay, Sarah Sheldon, Andrew W. Cross, and Christopher J. Wood

Subjects
Physics, QC1-999
Abstract

Hardware-efficient transpilation of quantum circuits to a quantum device native gate set is essential for the execution of quantum algorithms on noisy quantum computers. Typical quantum devices utilize a gate set with a single two-qubit Clifford entangling gate per pair of coupled qubits; however, in some applications access to a non-Clifford two-qubit gate can result in more optimal circuit decompositions and also allows more flexibility in optimizing over noise. We demonstrate calibration of a low-error non-Clifford controlled-π/2 phase (cs) gate on a cloud-based IBM Quantum system using the Qiskit Pulse framework. To measure the gate error of the calibrated cs gate we perform non-Clifford cnot-dihedral interleaved randomized benchmarking. We are able to obtain a gate error of 5.9(7)×10^{−3} at a gate length 263 ns, which is close to the coherence limit of the associated qubits, and lower error than the back-end standard calibrated cnot gate.

Published
2021
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6. Synthesis of CNOT-Dihedral circuits with optimal number of two qubit gates

Author

Shelly Garion and Andrew W. Cross

Subjects
Physics, QC1-999
Abstract

In this note we present explicit canonical forms for all the elements in the two-qubit CNOT-Dihedral group, with minimal numbers of controlled-$S$ ($CS$) and controlled-$X$ ($CX$) gates, using the generating set of quantum gates $[X, T, CX, CS]$. We provide an algorithm to successively construct the $n$-qubit CNOT-Dihedral group, asserting an optimal number of controlled-$X$ ($CX$) gates. These results are needed to estimate gate errors via non-Clifford randomized benchmarking and may have further applications to circuit optimization over fault-tolerant gate sets.

Published
2020
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7. Topological and Subsystem Codes on Low-Degree Graphs with Flag Qubits

Author

Christopher Chamberland, Guanyu Zhu, Theodore J. Yoder, Jared B. Hertzberg, and Andrew W. Cross

Subjects
Physics, QC1-999
Abstract

In this work we introduce two code families, which we call the heavy-hexagon code and the heavy-square code. Both code families are implemented by assigning physical data and ancilla qubits to both vertices and edges of low-degree graphs. Such a layout is particularly suitable for superconducting qubit architectures to minimize frequency collisions and cross talk. In some cases, frequency collisions can be reduced by several orders of magnitude. The heavy-hexagon code is a hybrid surface and Bacon-Shor code mapped onto a (heavy-) hexagonal lattice, whereas the heavy-square code is the surface code mapped onto a (heavy-) square lattice. In both cases, the lattice includes all the ancilla qubits required for fault-tolerant error correction. Naively, the limited qubit connectivity might be thought to limit the error-correcting capability of the code to less than its full distance. Therefore, essential to our construction is the use of flag qubits. We modify minimum-weight perfect-matching decoding to efficiently and scalably incorporate information from measurements of the flag qubits and correct up to the full code distance while respecting the limited connectivity. Simulations show that high threshold values for both codes can be obtained using our decoding protocol. Further, our decoding scheme can be adapted to other topological code families.

Published
2020
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8. Fault-tolerant magic state preparation with flag qubits

Author

Christopher Chamberland and Andrew W. Cross

Subjects
Physics, QC1-999
Abstract

Magic state distillation is one of the leading candidates for implementing universal fault-tolerant logical gates. However, the distillation circuits themselves are not fault-tolerant, so there is additional cost to first implement encoded Clifford gates with negligible error. In this paper we present a scheme to fault-tolerantly and directly prepare magic states using flag qubits. One of these schemes requires only three ancilla qubits, even with noisy Clifford gates. We compare the physical qubit and gate cost of our scheme to the magic state distillation protocol of Meier, Eastin, and Knill (MEK), which is efficient and uses a small stabilizer circuit. For low enough noise rates, we show that in some regimes the overhead can be improved by several orders of magnitude compared to the MEK scheme which uses Clifford operations encoded in the codes considered in this work.

Published
2019
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11. Quantum computing with Qiskit.

Author

Ali Javadi-Abhari, Matthew Treinish, Kevin Krsulich, Christopher J. Wood, Jake Lishman, Julien Gacon, Simon Martiel, Paul D. Nation, Lev S. Bishop, Andrew W. Cross, Blake R. Johnson, and Jay M. Gambetta

Published
2024
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30. Microwave-activated conditional-phase gate for superconducting qubits

Author

Jerry M Chow, Jay M Gambetta, Andrew W Cross, Seth T Merkel, Chad Rigetti, and M Steffen

Subjects
Science, Physics, QC1-999
Abstract

We introduce a new entangling gate between two fixed-frequency qubits statically coupled via a microwave resonator bus which combines the following desirable qualities: all-microwave control, appreciable qubit separation for reduction of crosstalk and leakage errors and the ability to function as a two-qubit conditional-phase gate. A fixed, always-on interaction is explicitly designed between higher energy (non-computational) states of two transmon qubits, and then a conditional-phase gate is ‘activated’ on the otherwise unperturbed qubit subspace via a microwave drive. We implement this microwave-activated conditional-phase gate with a fidelity from quantum process tomography of ∼ 87%.

Published
2013
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