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    <title>Quantum Computing: a Computer Scientist&#39;s Perspective on Scaling QC with Graph Rewriting</title>
    <link>http://localhost:1313/02_quantum/</link>
    <description>Recent content in Quantum Computing: a Computer Scientist&#39;s Perspective on Scaling QC with Graph Rewriting</description>
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      <title>Foundations of quantum computing</title>
      <link>http://localhost:1313/02_quantum/secbasics/</link>
      <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
      <guid>http://localhost:1313/02_quantum/secbasics/</guid>
      <description>&lt;p&gt;The most widespread computational model in quantum computing&amp;nbsp;&amp;ndash;&amp;nbsp;and arguably its&#xA;simplest&amp;nbsp;&amp;ndash;&amp;nbsp;is built on the qubit abstraction. As its name suggests, it is the&#xA;quantum analogue of the classical bit, i.e., a value that can take the values&#xA;&lt;code&gt;0&lt;/code&gt; or &lt;code&gt;1&lt;/code&gt;.&lt;/p&gt;&#xA;&lt;p&gt;We will stick to our promise of not delving into the details of the physical&#xA;realisations of qubits in real-world architectures. Nonetheless, it is important&#xA;to note one fundamental difference with classical systems. Classical bit values&#xA;(the famous &lt;code&gt;0&lt;/code&gt;s and &lt;code&gt;1&lt;/code&gt;s of our computers) are typically encoded using two&#xA;voltages; another way of saying this is that bit values, and hence data,&#xA;correspond to electrical currents in the wires&lt;sup id=&#34;92018ef5fnref:1&#34;&gt;&lt;a href=&#34;#92018ef5fn:1&#34; class=&#34;footnote-ref&#34; role=&#34;doc-noteref&#34;&gt;1&lt;/a&gt;&lt;/sup&gt; of a chip. Gates,&#xA;i.e. the lowest level of operations that can be applied to bits, then correspond&#xA;to barriers that let the electrical current flow through to outgoing wires, or&#xA;block it.&lt;/p&gt;</description>
    </item>
    <item>
      <title>Quantum circuit optimisation: a review</title>
      <link>http://localhost:1313/02_quantum/secquantum-sota/</link>
      <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
      <guid>http://localhost:1313/02_quantum/secquantum-sota/</guid>
      <description>&lt;p&gt;Much of the foundations of classical computer science rely on boolean logic and&#xA;discrete mathematics &lt;span class=&#34;citation&#34;&gt;&lt;span data-bibtex-key=&#34;Lehman2017&#34; class=&#34;citation-key&#34;&gt;Lehman, 2017&lt;/span&gt;&lt;span class=&#34;citation-full&#34;&gt;&lt;span class=&#34;authors&#34;&gt;Eric  &lt;span class=&#34;last-name&#34;&gt;Lehman&lt;/span&gt;, F. Thomson  &lt;span class=&#34;last-name&#34;&gt;Leighton&lt;/span&gt; and Albert R.  &lt;span class=&#34;last-name&#34;&gt;Meyer&lt;/span&gt;&lt;/span&gt;. 2017. &lt;em&gt;Mathematics for Computer Science&lt;/em&gt;. Samurai Media Limited&lt;/span&gt;&lt;/span&gt;. In some regards, this is a poor man&amp;rsquo;s maths,&#xA;as much of the structure that comes with continuous infinite mathematical&#xA;objects is lost along the way when discretised.&lt;/p&gt;&#xA;&lt;p&gt;In contrast, quantum computation, on the other hand, encompasses the whole&#xA;breadth of (finite dimensional) quantum physical system evolution. Underlying&#xA;this is a rich mathematical theory steeped in the theory of Hilbert spaces and&#xA;Lie groups&lt;sup id=&#34;e24f5a40fnref:1&#34;&gt;&lt;a href=&#34;#e24f5a40fn:1&#34; class=&#34;footnote-ref&#34; role=&#34;doc-noteref&#34;&gt;1&lt;/a&gt;&lt;/sup&gt;. A direct consequence of the mathematics of quantum&#xA;computations is the flourishing of an entire field of research dedicated to&#xA;quantum circuit optimisations &lt;span class=&#34;citation&#34;&gt;&lt;span data-bibtex-key=&#34;Karuppasamy2025&#34; class=&#34;citation-key&#34;&gt;Karupp., 2025&lt;/span&gt;&lt;span class=&#34;citation-full&#34;&gt;&lt;span class=&#34;authors&#34;&gt;Krishnageetha  &lt;span class=&#34;last-name&#34;&gt;Karuppasamy&lt;/span&gt;, Varun  &lt;span class=&#34;last-name&#34;&gt;Puram&lt;/span&gt;, Stevens  &lt;span class=&#34;last-name&#34;&gt;Johnson&lt;/span&gt; and Johnson P.  &lt;span class=&#34;last-name&#34;&gt;Thomas&lt;/span&gt;&lt;/span&gt;. 2025. A Comprehensive Review of Quantum Circuit Optimization: Current Trends and Future Directions. &lt;em&gt;Quantum Reports&lt;/em&gt; 7, 1 (January 2025, 2). &lt;span class=&#34;doi&#34;&gt;doi: &lt;a href=&#34;https://doi.org/10.3390/quantum7010002&#34;&gt;10.3390/quantum7010002&lt;/a&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;. They leverage the unique&#xA;structure and symmetries of quantum physics to reduce the noise and resource&#xA;requirements of quantum computations significantly.&lt;/p&gt;</description>
    </item>
    <item>
      <title>Rise of hybrid quantum-classical computation</title>
      <link>http://localhost:1313/02_quantum/sechybrid/</link>
      <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
      <guid>http://localhost:1313/02_quantum/sechybrid/</guid>
      <description>&lt;h3 id=&#34;quantum-measurements&#34;&gt;&#xA;  Quantum measurements&#xA;  &lt;a class=&#34;anchor&#34; href=&#34;#quantum-measurements&#34;&gt;#&lt;/a&gt;&#xA;&lt;/h3&gt;&#xA;&lt;p&gt;We have, until now, skipped over a crucial part of the quantum computation&#xA;process: the role of quantum measurements. Quantum data, in isolation, is&#xA;inherently inaccessible to us and the broader macroscopic world. A result from a&#xA;quantum computation is only of value if we can probe it and get some readout&#xA;value that we can display to the user or return to whoever launched the quantum&#xA;computation.&lt;/p&gt;</description>
    </item>
    <item>
      <title>Quantum compilers cannot do it alone</title>
      <link>http://localhost:1313/02_quantum/secneed-help/</link>
      <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
      <guid>http://localhost:1313/02_quantum/secneed-help/</guid>
      <description>&lt;p&gt;We have (hopefully!) by now convinced our readership that quantum programs must&#xA;interface with our established classical infrastructure and should rather be&#xA;understood as an interleaved execution of both classical and quantum operations.&#xA;The obvious question that thus poses itself is&lt;/p&gt;&#xA;&lt;!-- prettier-ignore --&gt;&#xA;&lt;blockquote class=&#34;book-hint info&#34;&gt;&#xA;&lt;p&gt;How do we equip quantum compilers to deal with classical operations?&lt;/p&gt;&#xA;&lt;!-- prettier-ignore --&gt;&#xA;&lt;/blockquote&gt;&#xA;&lt;p&gt;The simplest solution is to adopt the extended quantum circuit formalism with&#xA;support for classically controlled operations, as we have introduced in the&#xA;previous section. Using this representation, the basic types available for&#xA;computation are the qubit and the classical bit. We can also, at that point,&#xA;introduce purely classical operations on bits, for instance, to compute boolean&#xA;logic on measurement outcomes, such as &amp;ldquo;if both the first AND the second&#xA;measurement outcomes are &lt;code&gt;1&lt;/code&gt;, then &amp;hellip;&amp;rdquo;.&lt;/p&gt;</description>
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    <item>
      <title>Summary and further reading</title>
      <link>http://localhost:1313/02_quantum/seclitt/</link>
      <pubDate>Mon, 01 Jan 0001 00:00:00 +0000</pubDate>
      <guid>http://localhost:1313/02_quantum/seclitt/</guid>
      <description>&lt;p&gt;This introductory chapter covered some of the basic principles of quantum&#xA;computation and, in doing so, hopefully, made a convincing argument as to why we&#xA;should expect the programs running on quantum hardware to become more complex in&#xA;the future, with the intertwining of classical and quantum&#xA;computations&amp;nbsp;&amp;ndash;&amp;nbsp;processes we refer to as hybrid quantum-classical programs. Prior&#xA;to that, we also presented quantum compilation, an emerging discipline that is&#xA;introducing many new problems and ideas to the established corpus of work on&#xA;compiler research.&lt;/p&gt;</description>
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