List of quantum logic gates

In gate-based quantum computing, various sets of quantum logic gates are commonly used to express quantum operations. The following tables list several unitary quantum logic gates, together with their common name, how they are represented, and some of their properties. Controlled or conjugate transpose (adjoint) versions of some of these gates may not be listed.

Identity gate and global phase

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Name # qubits Operator symbol Matrix Circuit diagram Properties Refs
Identity,

no-op

1 (any)  , 𝟙    
or

 

[1]
Global phase 1 (any)  ,   or      
  • Continuous parameters:   (period  )
  • Exponential form:  
[1]

The identity gate is the identity operation  , most of the times this gate is not indicated in circuit diagrams, but it is useful when describing mathematical results.

It has been described as being a "wait cycle",[2] and a NOP.[3][1]

The global phase gate introduces a global phase   to the whole qubit quantum state. A quantum state is uniquely defined up to a phase. Because of the Born rule, a phase factor has no effect on a measurement outcome:   for any  .

Because   when the global phase gate is applied to a single qubit in a quantum register, the entire register's global phase is changed.

Also,  

These gates can be extended to any number of qubits or qudits.

Clifford qubit gates

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This table includes commonly used Clifford gates for qubits.[1][4][5]

Names # qubits Operator symbol Matrix Circuit diagram Some properties Refs
Pauli X,
NOT,
bit flip
1    

 
or
 

[1][6]
Pauli Y 1      
  • Hermitian
  • Pauli group
  • Traceless
  • Involutory
[1][6]
Pauli Z,
phase flip
1      
  • Hermitian
  • Pauli group
  • Traceless
  • Involutory
[1][6]
Phase gate S,
square root of Z
1       [1][6]
Square root of X,
square root of NOT
1  ,  ,       [1][7]
Hadamard,
Walsh-Hadamard
1      
  • Hermitian
  • Traceless
  • Involutory
[1][6]
Controlled NOT,
controlled-X,
controlled-bit flip,
reversible exclusive OR,
Feynman
2  ,    
 
 
  • Hermitian
  • Involutory

Implementation:

[1][6]
Anticontrolled-NOT,
anticontrolled-X,
zero control,
control-on-0-NOT,
reversible exclusive NOR
2  ,  ,      
  • Hermitian
  • Involutory
[1]
Controlled-Z,
controlled sign flip,
controlled phase flip
2  ,  ,  ,      
  • Hermitian
  • Involutory
  • Symmetrical

Implementation:

  • Duan-Kimble gate
[1][6]
Double-controlled NOT 2       [8]
Swap 2      
or
 
  • Hermitian
  • Involutory
  • Symmetrical
[1][6]
Imaginary swap 2      
or
 
  • Special unitary
  • Symmetrical
[1]

Other Clifford gates, including higher dimensional ones are not included here but by definition can be generated using   and  .

Note that if a Clifford gate A is not in the Pauli group,   or controlled-A are not in the Clifford gates.[citation needed]

The Clifford set is not a universal quantum gate set.

Non-Clifford qubit gates

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Relative phase gates

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Names # qubits Operator symbol Matrix Circuit diagram Properties Refs
Phase shift 1      
  • Continuous parameters:   (period  )
[9][10][11]
Phase gate T,
π/8 gate,
fourth root of Z
1   or       [1][6]
Controlled phase 2      
  • Continuous parameters:   (period  )
  • Symmetrical

Implementation:

[11]
Controlled phase S 2      
  • Symmetrical
[6]

The phase shift is a family of single-qubit gates that map the basis states   and  . The probability of measuring a   or   is unchanged after applying this gate, however it modifies the phase of the quantum state. This is equivalent to tracing a horizontal circle (a line of latitude), or a rotation along the z-axis on the Bloch sphere by   radians. A common example is the T gate where   (historically known as the   gate), the phase gate. Note that some Clifford gates are special cases of the phase shift gate:  

The argument to the phase shift gate is in U(1), and the gate performs a phase rotation in U(1) along the specified basis state (e.g.   rotates the phase about  ). Extending   to a rotation about a generic phase of both basis states of a 2-level quantum system (a qubit) can be done with a series circuit:  . When   this gate is the rotation operator   gate and if   it is a global phase.[a][b]

The T gate's historic name of   gate comes from the identity  , where  .

Arbitrary single-qubit phase shift gates   are natively available for transmon quantum processors through timing of microwave control pulses.[13] It can be explained in terms of change of frame.[14][15]

As with any single qubit gate one can build a controlled version of the phase shift gate. With respect to the computational basis, the 2-qubit controlled phase shift gate is: shifts the phase with   only if it acts on the state  :

 

The controlled-Z (or CZ) gate is the special case where  .

The controlled-S gate is the case of the controlled-  when   and is a commonly used gate.[6]

Rotation operator gates

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Names # qubits Operator symbol Exponential form Matrix Circuit diagram Properties Refs
Rotation about x-axis 1        
  • Special unitary
  • Continuous parameters:   (period  )
[1][6]
Rotation about y-axis 1        
  • Special unitary
  • Continuous parameters:   (period  )
[1][6]
Rotation about z-axis 1        
  • Special unitary
  • Continuous parameters:   (period  )
[1][6]

The rotation operator gates   and   are the analog rotation matrices in three Cartesian axes of SO(3),[c] along the x, y or z-axes of the Bloch sphere projection.

As Pauli matrices are related to the generator of rotations, these rotation operators can be written as matrix exponentials with Pauli matrices in the argument. Any   unitary matrix in SU(2) can be written as a product (i.e. series circuit) of three rotation gates or less. Note that for two-level systems such as qubits and spinors, these rotations have a period of . A rotation of (360 degrees) returns the same statevector with a different phase.[16]

We also have   and   for all  

The rotation matrices are related to the Pauli matrices in the following way:  

It's possible to work out the adjoint action of rotations on the Pauli vector, namely rotation effectively by double the angle a to apply Rodrigues' rotation formula:

 

Taking the dot product of any unit vector with the above formula generates the expression of any single qubit gate when sandwiched within adjoint rotation gates. For example, it can be shown that  . Also, using the anticommuting relation we have  .

Rotation operators have interesting identities. For example,   and   Also, using the anticommuting relations we have   and  

Global phase and phase shift can be transformed into each other's with the Z-rotation operator:  .[5]: 11 [1]: 77–83 

The   gate represents a rotation of π/2 about the x axis at the Bloch sphere  .

Similar rotation operator gates exist for SU(3) using Gell-Mann matrices. They are the rotation operators used with qutrits.

Two-qubit interaction gates

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Names # qubits Operator symbol Exponential form Matrix Circuit diagram Properties Refs
XX interaction 2  ,      
  • Special unitary
  • Continuous parameters:   (period  )

Implementation:

[citation needed]
YY interaction 2  ,      
  • Special unitary
  • Continuous parameters:   (period  )

Implementation:

[citation needed]
ZZ interaction 2  ,      
  • Special unitary
  • Continuous parameters:   (period  )
[citation needed]
XY,
XX plus YY
2  ,      
  • Special unitary
  • Continuous parameters:   (period  )
[citation needed]

The qubit-qubit Ising coupling or Heisenberg interaction gates Rxx, Ryy and Rzz are 2-qubit gates that are implemented natively in some trapped-ion quantum computers, using for example the Mølmer–Sørensen gate procedure.[17][18]

Note that these gates can be expressed in sinusoidal form also, for example  .

The CNOT gate can be further decomposed as products of rotation operator gates and exactly a single two-qubit interaction gate, for example

 

The SWAP gate can be constructed from other gates, for example using the two-qubit interaction gates:  .

In superconducting circuits, the family of gates resulting from Heisenberg interactions is sometimes called the fSim gate set. They can be realized using flux-tunable qubits with flux-tunable coupling,[19] or using microwave drives in fixed-frequency qubits with fixed coupling.[20]

Non-Clifford swap gates

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Names # qubits Operator symbol Matrix Circuit diagram Properties Refs
Square root swap 2       [1]
Square root imaginary swap 2    
  • Special unitary
[11]
Swap (raised to a power) 2      
  • Continuous parameters:   (period  )
[1]
Fredkin,

controlled swap

3  ,      
or
 
  • Hermitian
  • Involutory
  • Functionally complete reversible gate for Boolean algebra
[1][6]

The SWAP gate performs half-way of a two-qubit swap (see Clifford gates). It is universal such that any many-qubit gate can be constructed from only SWAP and single qubit gates. More than one application of the SWAP is required to produce a Bell state from product states. The SWAP gate arises naturally in systems that exploit exchange interaction.[21][1]

For systems with Ising like interactions, it is sometimes more natural to introduce the imaginary swap[22] or iSWAP.[23][24] Note that   and  , or more generally   for all real n except 0.

SWAPα arises naturally in spintronic quantum computers.[1]

The Fredkin gate (also CSWAP or CS gate), named after Edward Fredkin, is a 3-bit gate that performs a controlled swap. It is universal for classical computation. It has the useful property that the numbers of 0s and 1s are conserved throughout, which in the billiard ball model means the same number of balls are output as input.

Other named gates

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Names # qubits Operator symbol Matrix Circuit diagram Properties Named after Refs
General single qubit rotation 1    
  • Implements an arbitrary single-qubit rotation
  • Continuous parameters:   (period  )
OpenQASM U gate[d] [11][25]
Barenco 2    
  • Implements a controlled arbitrary qubit rotation
  • Universal quantum gate
  • Continuous parameters:   (period  )
Adriano Barenco [1]
Berkeley B 2    
  • Special unitary
  • Exponential form:
 
University of California Berkeley[26] [1]
Controlled-V,

controlled square root NOT

2       [9]
Core entangling,

canonical decomposition

2  ,    
  • Special unitary
  • Universal quantum gate
  • Exponential form
 
  • Continuous parameters:   (period  )
[1]
Dagwood Bumstead 2    
  • Special unitary
  • Exponential form:
 
Comicbook Dagwood Bumstead[27] [28][27]
Echoed cross resonance 2    
  • Special unitary
[29]
Fermionic simulation 2  ,    
  • Special unitary
  • Continuous parameters:   (period  )
[30][19][20]
Givens 2  ,    
  • Special unitary
  • Exponential form:
 
  • Continuous parameters:   (period  )
Givens rotations [31]
Magic 2     [1]
Sycamore 2  ,     Google's Sycamore processor [32]
CZ-SWAP 2  ,  
  • Continuous parameters:  
  • Submatrix of a controlled-CZS (CCZS)
[33]
Deutsch 3  ,    
  • Continuous parameters:   (period  )
  • Universal quantum gate
David Deutsch [1]
Margolus,
simplified Toffoli
3  ,      
  • Hermitian
  • Involutory
  • Special unitary
  • Functionally complete reversible gate for Boolean algebra
Norman Margolus [34][35]
Peres 3  ,     
  • Functionally complete reversible gate for Boolean algebra
Asher Peres [36]
Toffoli,
controlled-controlled NOT
3      
  • Hermitian
  • Involutory
  • Functionally complete reversible gate for Boolean algebra
Tommaso Toffoli [1][6]

Fermionic-Fredkin,

Controlled-fermionic SWAP

3  ,

 ,  

  [33]

[37]

Notes

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  1. ^   when  , where   is the conjugate transpose (or Hermitian adjoint).
  2. ^ Also:  
  3. ^ a SU(2) double cover. See also Hopf fibration.
  4. ^ The matrix shown here is from openQASM 3.0, which differs from   from a global phase (OpenQASM 2.0 U gate is in SU(2) ) .

References

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  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae Williams, Colin P. (2011). Explorations in Quantum Computing. Springer. ISBN 978-1-84628-887-6.
  2. ^ "IGate". qiskit.org. Qiskit online documentation.
  3. ^ "I operation". docs.microsoft.com. 28 July 2023. Q# online documentation.
  4. ^ Feynman, Richard P. (1986). "Quantum mechanical computers". Foundations of Physics. 16 (6). Springer Science and Business Media LLC: 507–531. Bibcode:1986FoPh...16..507F. doi:10.1007/bf01886518. ISSN 0015-9018. S2CID 122076550.
  5. ^ a b Barenco, Adriano; Bennett, Charles H.; Cleve, Richard; DiVincenzo, David P.; Margolus, Norman; Shor, Peter; Sleator, Tycho; Smolin, John A.; Weinfurter, Harald (1995-11-01). "Elementary gates for quantum computation". Physical Review A. 52 (5). American Physical Society (APS): 3457–3467. arXiv:quant-ph/9503016. Bibcode:1995PhRvA..52.3457B. doi:10.1103/physreva.52.3457. ISSN 1050-2947. PMID 9912645. S2CID 8764584.
  6. ^ a b c d e f g h i j k l m n o p Nielsen, Michael A. (2010). Quantum computation and quantum information. Isaac L. Chuang (10th anniversary ed.). Cambridge: Cambridge University Press. ISBN 978-1-107-00217-3. OCLC 665137861.
  7. ^ Hung, W.N.N.; Xiaoyu Song; Guowu Yang; Jin Yang; Perkowski, M. (September 2006). "Optimal synthesis of multiple output Boolean functions using a set of quantum gates by symbolic reachability analysis". IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems. 25 (9): 1652–1663. doi:10.1109/tcad.2005.858352. ISSN 0278-0070. S2CID 14123321.
  8. ^ Collins, Daniel; Linden, Noah; Popescu, Sandu (2001-08-07). "Nonlocal content of quantum operations". Physical Review A. 64 (3): 032302. arXiv:quant-ph/0005102. Bibcode:2001PhRvA..64c2302C. doi:10.1103/PhysRevA.64.032302. ISSN 1050-2947. S2CID 29769034.
  9. ^ a b Pathak, Anirban (2013-06-20). Elements of Quantum Computation and Quantum Communication. Taylor & Francis. ISBN 978-1-4665-1792-9.
  10. ^ Yanofsky, Noson S.; Mannucci, Mirco A. (2008-08-11). Quantum Computing for Computer Scientists. Cambridge University Press. ISBN 978-1-139-64390-0.
  11. ^ a b c d Stancil, Daniel D.; Byrd, Gregory T. (2022-04-19). Principles of Superconducting Quantum Computers. John Wiley & Sons. ISBN 978-1-119-75074-1.
  12. ^ D. Jaksch, J. I. Cirac, P. Zoller, S. L. Rolston, R. Côté, and M. D. Lukin (2000). "Fast Quantum Gates for Neutral Atoms". Phys. Rev. Lett. 85 (10): 2208–2211. arXiv:quant-ph/0004038. Bibcode:2000PhRvL..85.2208J. doi:10.1103/PhysRevLett.85.2208. PMID 10970499.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ Dibyendu Chatterjee, Arijit Roy (2015). "A transmon-based quantum half-adder scheme". Progress of Theoretical and Experimental Physics. 2015 (9): 7–8. Bibcode:2015PTEP.2015i3A02C. doi:10.1093/ptep/ptv122.
  14. ^ McKay, David C.; Wood, Christopher J.; Sheldon, Sarah; Chow, Jerry M.; Gambetta, Jay M. (31 August 2017). "Efficient Z gates for quantum computing". Physical Review A. 96 (2): 022330. arXiv:1612.00858. Bibcode:2015PTEP.2015i3A02C. doi:10.1093/ptep/ptv122.
  15. ^ "qiskit.circuit.library.PhaseGate". IBM (qiskit documentation).
  16. ^ Griffiths, D. J. (2008). Introduction to Elementary Particles (2nd ed.). John Wiley & Sons. pp. 127–128. ISBN 978-3-527-40601-2.
  17. ^ "Monroe Conference" (PDF). online.kitp.ucsb.edu.
  18. ^ "Demonstration of a small programmable quantum computer with atomic qubits" (PDF). Retrieved 2019-02-10.
  19. ^ a b Foxen, B.; Neill, C.; Dunsworth, A.; Roushan, P.; Chiaro, B.; Megrant, A.; Kelly, J.; Chen, Zijun; Satzinger, K.; Barends, R.; Arute, F.; Arya, K.; Babbush, R.; Bacon, D.; Bardin, J. C.; Boixo, S.; Buell, D.; Burkett, B.; Chen, Yu; Collins, R.; Farhi, E.; Fowler, A.; Gidney, C.; Giustina, M.; Graff, R.; Harrigan, M.; Huang, T.; Isakov, S. V.; Jeffrey, E.; Jiang, Z.; Kafri, D.; Kechedzhi, K.; Klimov, P.; Korotkov, A.; Kostritsa, F.; Landhuis, D.; Lucero, E.; McClean, J.; McEwen, M.; Mi, X.; Mohseni, M.; Mutus, J. Y.; Naaman, O.; Neeley, M.; Niu, M.; Petukhov, A.; Quintana, C.; Rubin, N.; Sank, D.; Smelyanskiy, V.; Vainsencher, A.; White, T. C.; Yao, Z.; Yeh, P.; Zalcman, A.; Neven, H.; Martinis, J. M. (2020-09-15). "Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms". Physical Review Letters. 125 (12): 120504. arXiv:2001.08343. Bibcode:2020PhRvL.125l0504F. doi:10.1103/PhysRevLett.125.120504. ISSN 0031-9007. PMID 33016760.
  20. ^ a b Nguyen, L.B.; Kim, Y.; Hashim, A.; Goss, N.; Marinelli, B.; Bhandari, B.; Das, D.; Naik, R.K.; Kreikebaum, J.M.; Jordan, A.; Santiago, D.I.; Siddiqi, I. (16 January 2024). "Programmable Heisenberg interactions between Floquet qubits". Nature Physics. 20 (1): 240–246. arXiv:2211.10383. Bibcode:2024NatPh..20..240N. doi:10.1038/s41567-023-02326-7.
  21. ^ Nemirovsky, Jonathan; Sagi, Yoav (2021), "Fast universal two-qubit gate for neutral fermionic atoms in optical tweezers", Physical Review Research, 3 (1): 013113, arXiv:2008.09819, Bibcode:2021PhRvR...3a3113N, doi:10.1103/PhysRevResearch.3.013113
  22. ^ Rasmussen, S. E.; Zinner, N. T. (2020-07-17). "Simple implementation of high fidelity controlled- i swap gates and quantum circuit exponentiation of non-Hermitian gates". Physical Review Research. 2 (3): 033097. arXiv:2002.11728. Bibcode:2020PhRvR...2c3097R. doi:10.1103/PhysRevResearch.2.033097. ISSN 2643-1564.
  23. ^ Schuch, Norbert; Siewert, Jens (2003-03-10). "Natural two-qubit gate for quantum computation using the XY interaction". Physical Review A. 67 (3): 032301. arXiv:quant-ph/0209035. Bibcode:2003PhRvA..67c2301S. doi:10.1103/PhysRevA.67.032301. ISSN 1050-2947. S2CID 50823541.
  24. ^ Dallaire-Demers, Pierre-Luc; Wilhelm, Frank K. (2016-12-05). "Quantum gates and architecture for the quantum simulation of the Fermi-Hubbard model". Physical Review A. 94 (6): 062304. arXiv:1606.00208. Bibcode:2016PhRvA..94f2304D. doi:10.1103/PhysRevA.94.062304. ISSN 2469-9926. S2CID 118408193.
  25. ^ Cross, Andrew; Javadi-Abhari, Ali; Alexander, Thomas; De Beaudrap, Niel; Bishop, Lev S.; Heidel, Steven; Ryan, Colm A.; Sivarajah, Prasahnt; Smolin, John; Gambetta, Jay M.; Johnson, Blake R. (2022). "OpenQASM 3: A Broader and Deeper Quantum Assembly Language". ACM Transactions on Quantum Computing. 3 (3): 1–50. arXiv:2104.14722. doi:10.1145/3505636. ISSN 2643-6809. S2CID 233476587.
  26. ^ Zhang, Jun; Vala, Jiri; Sastry, Shankar; Whaley, K. Birgitta (2004-07-07). "Minimum Construction of Two-Qubit Quantum Operations". Physical Review Letters. 93 (2): 020502. arXiv:quant-ph/0312193. Bibcode:2004PhRvL..93b0502Z. doi:10.1103/PhysRevLett.93.020502. ISSN 0031-9007. PMID 15323888. S2CID 9632700.
  27. ^ a b AbuGhanem, M. (2021-01-01). "Two-qubit Entangling Gate for Superconducting Quantum Computers". Rochester, NY. doi:10.2139/ssrn.4188257. S2CID 252264545. SSRN 4188257. {{cite journal}}: Cite journal requires |journal= (help)
  28. ^ Peterson, Eric C.; Crooks, Gavin E.; Smith, Robert S. (2020-03-26). "Fixed-Depth Two-Qubit Circuits and the Monodromy Polytope". Quantum. 4: 247. arXiv:1904.10541. doi:10.22331/q-2020-03-26-247. S2CID 214690323.
  29. ^ Córcoles, A. D.; Magesan, Easwar; Srinivasan, Srikanth J.; Cross, Andrew W.; Steffen, M.; Gambetta, Jay M.; Chow, Jerry M. (2015-04-29). "Demonstration of a quantum error detection code using a square lattice of four superconducting qubits". Nature Communications. 6 (1): 6979. arXiv:1410.6419. Bibcode:2015NatCo...6.6979C. doi:10.1038/ncomms7979. ISSN 2041-1723. PMC 4421819. PMID 25923200.
  30. ^ Kyriienko, Oleksandr; Elfving, Vincent E. (2021-11-15). "Generalized quantum circuit differentiation rules". Physical Review A. 104 (5): 052417. arXiv:2108.01218. Bibcode:2021PhRvA.104e2417K. doi:10.1103/PhysRevA.104.052417. hdl:10871/127818. ISSN 2469-9926. S2CID 236881494.
  31. ^ Arrazola, Juan Miguel; Matteo, Olivia Di; Quesada, Nicolás; Jahangiri, Soran; Delgado, Alain; Killoran, Nathan (2022-06-20). "Universal quantum circuits for quantum chemistry". Quantum. 6: 742. arXiv:2106.13839. Bibcode:2022Quant...6..742A. doi:10.22331/q-2022-06-20-742. S2CID 235658488.
  32. ^ Arute, Frank; Arya, Kunal; Babbush, Ryan; Bacon, Dave; Bardin, Joseph C.; Barends, Rami; Biswas, Rupak; Boixo, Sergio; Brandao, Fernando G. S. L.; Buell, David A.; Burkett, Brian; Chen, Yu; Chen, Zijun; Chiaro, Ben; Collins, Roberto (2019). "Quantum supremacy using a programmable superconducting processor". Nature. 574 (7779): 505–510. arXiv:1910.11333. Bibcode:2019Natur.574..505A. doi:10.1038/s41586-019-1666-5. ISSN 1476-4687. PMID 31645734. S2CID 204836822.
  33. ^ a b Gu, Xiu; Fernández-Pendás, Jorge; Vikstål, Pontus; Abad, Tahereh; Warren, Christopher; Bengtsson, Andreas; Tancredi, Giovanna; Shumeiko, Vitaly; Bylander, Jonas; Johansson, Göran; Frisk Kockum, Anton (2021). "Fast Multiqubit Gates through Simultaneous Two-Qubit Gates". PRX Quantum. 2 (4): 040348. arXiv:2108.11358. Bibcode:2021PRXQ....2d0348G. doi:10.1103/PRXQuantum.2.040348. ISSN 2691-3399.
  34. ^ Maslov, Dmitri (2016-02-10). "Advantages of using relative-phase Toffoli gates with an application to multiple control Toffoli optimization". Physical Review A. 93 (2): 022311. arXiv:1508.03273. Bibcode:2016PhRvA..93b2311M. doi:10.1103/PhysRevA.93.022311. ISSN 2469-9926. S2CID 5226873.
  35. ^ Song, Guang; Klappenecker, Andreas (2003-12-31). "The simplified Toffoli gate implementation by Margolus is optimal". arXiv:quant-ph/0312225. Bibcode:2003quant.ph.12225S. {{cite journal}}: Cite journal requires |journal= (help)
  36. ^ Thapliyal, Himanshu; Ranganathan, Nagarajan (2009). "Design of Efficient Reversible Binary Subtractors Based on a New Reversible Gate". 2009 IEEE Computer Society Annual Symposium on VLSI. pp. 229–234. doi:10.1109/ISVLSI.2009.49. ISBN 978-1-4244-4408-3. S2CID 16182781.
  37. ^ Warren, Christopher; Fernández-Pendás, Jorge; Ahmed, Shahnawaz; Abad, Tahereh; Bengtsson, Andreas; Biznárová, Janka; Debnath, Kamanasish; Gu, Xiu; Križan, Christian; Osman, Amr; Fadavi Roudsari, Anita; Delsing, Per; Johansson, Göran; Frisk Kockum, Anton; Tancredi, Giovanna; Bylander, Jonas (2023). "Extensive characterization and implementation of a family of three-qubit gates at the coherence limit". npj Quantum Information. 9 (1): 44. arXiv:2207.02938. Bibcode:2023npjQI...9...44W. doi:10.1038/s41534-023-00711-x. ISSN 2056-6387.