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QCL (Quantum Computing Language)

QCL is one of the first implemented quantum programming languages


This is a github port from the project's official homepage. The idea is to ease the contribution of programmers interested in quantum computing, through guides, documentation, tests and the development of the core language itself.

Original README by Bernhard Oemer

Despite many common concepts with classical computer science, quantum computing is still widely considered as a special discipline within the broad field of theoretical physics. One reason for the slow adoption of QC by the computer science community is the confusing variety of formalisms (Dirac notation, matrices, gates, operators, etc.), none of which has any similarity with classical programming languages, as well as the rather "physical" terminology in most of the available literature.

QCL (Quantum Computation Language) tries to fill this gap: QCL is a high level, architecture independent programming language for quantum computers, with a syntax derived from classical procedural languages like C or Pascal. This allows for the complete implementation and simulation of quantum algorithms (including classical components) in one consistent formalism.


  • a classical control language with functions, flow-control, interactive i/o and various classical data types (int, real, complex, boolean, string)
  • 2 quantum operator types: general unitarian (operator) and reversible pseudo-classic gates (qufunct)
  • inverse execution, allowing for on-the-fly determination of the inverse operator though caching of operator calls
  • various quantum data types (qubit registers) for compile time information on access modes (qureg, quconst, quvoid, quscratch)
  • convenient functions to manipulate quantum registers (q[n] - qubit, q[n:m] - substring, q&p - combined register)
  • Quantum memory management (quheap) allowing for local quantum variables
  • Transparent integration of Bennet-style scratch space management
  • Easy adaption to individual sets of elementary operators
  • graphical output for (X11 and Postscript) (v0.5)
  • conditional operators and quantum if-statements (v0.5, experimental)


QCL has been developed under Linux; version 0.5.1 is tested to compile with the GNU C++ compiler 2.95.3 under SuSE 7.3. It should - however - compile under any Unix system with minor modifications (see the Makefile for details).

The current version of QCL (sources and i386 Linux binaries) is available from my homepage:


The reference documentation for QCL is my master thesis in technical physics "A Procedural Formalism for Quantum Computing". It gives a complete reference to QCL with many examples and also features a brief introduction into Quantum Computing. Some knowledge about Quantum Physics and familiarity with the braket-formalism is required.

A more basic introduction esp. for computing scientists to quantum computing, quantum algorithms and QCL is included in my CS master thesis "Quantum Programming in QCL" which also features an introductory chapter to quantum physics in general.

Both documents are available online in Postscript or HTML format:


Besides the usual C++ development tools, you will need to have flex, bison and (optionally) GNU readline installed on your system.

Untar the source package, then cd to the QCL directory, edit the Makefile for your needs and type

  make install

This will, by default, install the binary qcl to /usr/local/bin and the QCL include files to /usr/local/lib/qcl.

For plotting support, libplotter (the C++ bindings of of GNU libplot) is required. GNU libplot is part of the the GNU plotutils; see

Since version 0.4.3, QCL also includes support for the TeXmacs mathematical text editor. Recent TeXmacs distributions ( or newer) already provide the necessary interfaces, so no additional installation is required. You can get the latest TeXmacs sources from


Andrey G. Grozin

  • initial TeXmacs support
  • color XTerm support

Muhammad Hussain Yusuf

  • maintainer of the debian QCL package
  • testing of QCL on many hardware plattforms


If you encounter any bugs or miss any particular feature or just like QCL, please let me know. My email address is

The QCL interpreter is Open Source(tm) software, so please feel free to write your own ports and extentions. If you send me patches, I will most probably include them in future versions of QCL and maintain them to the best of my abilities. ;-) Since English isn't my native language, I also appreciate any orthographic and grammatical corrections.

Bernhard Oemer