Quil (instruction set architecture)

<h2 id="underlying-quantum-abstract-machine">Underlying quantum abstract machine</h2>
<p>In the paper presented by Smith, Curtis and Zeng, Quil specifies the <a href="/facts/Instruction_set_architecture/8p8vwUeE">instruction set</a> for a Quantum Abstract Machine (QAM,) akin to a Turing machine, yet more practical for accomplishing "real-world" tasks.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> The state of the QAM can be represented as a 6-<a href="/facts/Tuple/BI1HIxL8">tuple</a> 
  
    
      
        (
        
          |
        
        Ψ
        ⟩
        ,
        C
        ,
        G
        ,
        
          G
          ′
        
        ,
        P
        ,
        κ
        )
      
    
    {\displaystyle (|\Psi \rangle ,C,G,G',P,\kappa )}
  
 where:
</p>
<ul><li>
  
    
      
        
          |
        
        Ψ
        ⟩
      
    
    {\displaystyle |\Psi \rangle }
  
 is the (quantum) state of a fixed but <a href="/facts/Arbitrariness/4SBLd8Q7">arbitrary</a> number of <a href="/facts/Qubit/WveeEubw">qubits</a> 
  
    
      
        
          N
          
            q
          
        
      
    
    {\displaystyle N_{q}}
  
 indexed using a <a href="/facts/0-based_indexing/DITPGFHR">0-based indexing</a>.</li>
<li>
  
    
      
        C
      
    
    {\displaystyle C}
  
 is a classical <a href="/facts/Computer_memory/hQKVQ51J">memory</a> of a number 
  
    
      
        
          N
          
            c
          
        
      
    
    {\displaystyle N_{c}}
  
 of classical <a href="/facts/Bit/S972NSaD">bits</a> indexed using a 0-based indexing.</li>
<li>
  
    
      
        G
      
    
    {\displaystyle G}
  
 a fixed but arbitrary list of static gates (<a href="/facts/Quantum_logic_gate/EFV5sPCU">quantum gates</a> that do not depend on parameters, like the <a href="/facts/Hadamard_gate/JFD5uojA">Hadamard gate</a>.)</li>
<li>
  
    
      
        
          G
          ′
        
      
    
    {\displaystyle G'}
  
 a fixed but arbitrary list of parametric gates (gates that depend on a number of <a href="/facts/Complex_number/2w7mqI7e">complex</a> parameters like the <a href="/facts/Phase_shift_gate/EFV5sPCU">phase shift gate</a> that requires an angle <a href="/facts/Parameter_(computer_programming)/LcuLbbSq">parameter</a> to be completely defined.)</li>
<li>
  
    
      
        P
      
    
    {\displaystyle P}
  
 a sequence of Quil instructions to be executed, representing the program. The length of 
  
    
      
        P
      
    
    {\displaystyle P}
  
 is denoted by 
  
    
      
        
          |
        
        P
        
          |
        
      
    
    {\displaystyle |P|}
  
.</li>
<li>
  
    
      
        κ
      
    
    {\displaystyle \kappa }
  
 an integer <a href="/facts/Program_counter/BxqulBRq">program counter</a> pointing to the next instruction to be executed. 
  
    
      
        κ
      
    
    {\displaystyle \kappa }
  
 always starts at 0 (pointing to the 
  
    
      
        
          0
          
            t
            h
          
        
      
    
    {\displaystyle 0^{th}}
  
 instruction) and ends at 
  
    
      
        
          |
        
        P
        
          |
        
      
    
    {\displaystyle |P|}
  
 indicating program halting (note that the last instruction has the index 
  
    
      
        
          |
        
        P
        
          |
        
        −
        1
      
    
    {\displaystyle |P|-1}
  
.) The program counter is incremented after every instruction, except for special <a href="/facts/Control_flow/2XTDfErC">control flow</a> instructions (conditional and unconditional <a href="/facts/Jump_(computer_science)/obBGrnor">jumps</a>, and the special HALT instruction that halts the program by setting 
  
    
      
        κ
      
    
    {\displaystyle \kappa }
  
 to 
  
    
      
        
          |
        
        P
        
          |
        
      
    
    {\displaystyle |P|}
  
.</li></ul>
<p>The <a href="/facts/Semantics_(computer_science)/JEP1zyBv">semantics</a> of the QAM are defined using <a href="/facts/Tensor_product/7K3pR1ap">tensor products</a> of <a href="/facts/Hilbert_space/aDFMh4lV">Hilbert spaces</a> and the <a href="/facts/Linear_map/Q1PBKNVV">linear maps</a> between them.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a>
</p>
<h2 id="features">Features</h2>
<p>Quil has support for defining possibly parametrized gates in matrix form (the language does not include a way to verify that the matrices are <a href="/facts/Unitary_matrix/8fsxv3KD">unitary</a>, which is a necessary condition for the physical realizability of the defined gate) and their application on qubits. The language also supports <a href="/facts/Macro_(computer_science)/7abAsm1o">macro</a>-like definitions of possibly parametrized <a href="/facts/Quantum_circuit/yuFDFFPa">quantum circuits</a> and their expansion, qubit <a href="/facts/Measurement_in_quantum_mechanics/VY7jPfP0">measurement</a> and recording of the outcome in classical memory, synchronization with classical computers with the WAIT instruction which pauses the execution of a Quil program until a classical program has ended its execution, conditional and unconditional <a href="/facts/Branch_(computer_science)/obBGrnor">branching</a>, <a href="/facts/Pragma_(programming)/RsozxGG0">pragma</a> support, as well as inclusion of files for use as <a href="/facts/Library_(computing)/xRzL3P7q">libraries</a> (a standard set of gates is provided as one of the libraries.)
</p>
<h2 id="rigetti-qvm">Rigetti QVM</h2>
<p>Rigetti Computing developed a quantum <a href="/facts/Virtual_machine/BLevU3sx">virtual machine</a> in <a href="/facts/Common_Lisp/mq1pRbSF">Common Lisp</a> that simulates the defined Quantum Abstract Machine on a classical computer and is capable of the <a href="/facts/Parsing/nRKB01S3">parsing</a> and execution of Quil programs with possibly remote execution via HTTP.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a>
</p>
<h2 id="example">Example</h2>
<p>The following example demonstrates the classical control flow needed to do <a href="/facts/Quantum_teleportation/2lWvQA4F">quantum teleportation</a> of the <a href="/facts/Qubit/WveeEubw">qubit</a> in <a href="/facts/Processor_register/32RvbUdz">register</a> 2 to register 1:<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a>
</p>
# Declare classical memory
DECLARE ro BIT[2]
# Create Bell Pair
H 0
CNOT 0 1
# Teleport
CNOT 2 0
H 2
MEASURE 2 ro[0]
MEASURE 0 ro[1]
# Classically communicate measurements
JUMP-UNLESS @SKIP ro[1]
X 1
LABEL @SKIP
JUMP-UNLESS @END ro[0]
Z 1
LABEL @END
<p>Examples of the implementations of the <a href="/facts/Quantum_Fourier_transform/pT71oCV7">quantum fourier transform</a> and the variational quantum <a href="/facts/Eigensolver/AYecadB0">Eigensolver</a> are given in the paper.
</p>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://github.com/quil-lang/quil">quil</a> on <a href="/facts/GitHub/n1hNCsc3">GitHub</a>  GitHub repository</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Smith, Robert S.; Curtis, Michael J.; Zeng, William J. (2016-08-10). "A Practical Quantum Instruction Set Architecture". arXiv:1608.03355 [quant-ph]. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>McClean, Jarrod R.; Romero, Jonathan; Babbush, Ryan; Aspuru-Guzik, Alán (2016-02-04). "The theory of variational hybrid quantum-classical algorithms". New Journal of Physics. 18 (2): 023023. arXiv:1509.04279. Bibcode:2016NJPh...18b3023M. doi:10.1088/1367-2630/18/2/023023. ISSN 1367-2630. S2CID 92988541. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Rubin, Nicholas C. (2016-10-21). "A Hybrid Classical/Quantum Approach for Large-Scale Studies of Quantum Systems with Density Matrix Embedding Theory". arXiv:1610.06910 [quant-ph]. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Farhi, Edward; Goldstone, Jeffrey; Gutmann, Sam (2014-11-14). "A Quantum Approximate Optimization Algorithm". arXiv:1411.4028 [quant-ph]. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>"Rigetti Launches Full-Stack Quantum Computing Service and Quantum IC Fab". IEEE Spectrum: Technology, Engineering, and Science News. 26 June 2017. Retrieved 2017-07-06. <a href="https://spectrum.ieee.org/rigetti-launches-fullstack-quantum-computing-service-and-quantum-ic-fab" target="_blank">https://spectrum.ieee.org/rigetti-launches-fullstack-quantum-computing-service-and-quantum-ic-fab</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>"Rigetti Quietly Releases Beta of Forest Platform for Quantum Programming in the Cloud | Quantum Computing Report". quantumcomputingreport.com. 8 March 2017. Retrieved 2017-07-06. <a href="https://quantumcomputingreport.com/news/rigetti-quietly-releases-beta-of-forest-platform-for-quantum-programming-in-the-cloud/" target="_blank">https://quantumcomputingreport.com/news/rigetti-quietly-releases-beta-of-forest-platform-for-quantum-programming-in-the-cloud/</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"XACC Rigetti Accelerator". ornl-qci.github.io. Retrieved 2017-07-06. <a href="https://ornl-qci.github.io/xacc/accelerators/rigetti" target="_blank">https://ornl-qci.github.io/xacc/accelerators/rigetti</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>Doiron, Nick (2017-03-07), jsquil: Quantum computer instructions for JavaScript developers, retrieved 2017-07-06 <a href="https://github.com/mapmeld/jsquil" target="_blank">https://github.com/mapmeld/jsquil</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>Smith, Robert S.; Curtis, Michael J.; Zeng, William J. (2016-08-10). "A Practical Quantum Instruction Set Architecture". arXiv:1608.03355 [quant-ph]. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
<li id="fn:10"><p>Smith, Robert S.; Curtis, Michael J.; Zeng, William J. (2016-08-10). "A Practical Quantum Instruction Set Architecture". arXiv:1608.03355 [quant-ph]. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li>
<li id="fn:11"><p>The @rigetti high-performance quantum virtual machine.: rigetti/qvm, Rigetti Computing, 2019-04-26, retrieved 2019-04-28 <a href="https://github.com/rigetti/qvm" target="_blank">https://github.com/rigetti/qvm</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li>
<li id="fn:12"><p>Nielsen, Michael A.; Chuang, Isaac L. (2000). Quantum Computation and Quantum Information. Cambridge University Press. p. 27. ISBN 978-0-521-63503-5. <a href="978-0-521-63503-5" target="_blank">978-0-521-63503-5</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li>
<li id="fn:13"><p>Computing, Rigetti (28 May 2019). "pyQuil Documentation" (PDF). pyQuil Documentaion. Retrieved 6 June 2019. <a href="https://media.readthedocs.org/pdf/pyquil/latest/pyquil.pdf" target="_blank">https://media.readthedocs.org/pdf/pyquil/latest/pyquil.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li>
</ol>

Quil (instruction set architecture) open-in-new

Quil (instruction set architecture)