Quantum and CircuitsReading edition

From the cut to a numerical lower bound

Reading tools
Reading libraryFind statementsInspect Lean
Switch work

Saved reading

Read side by side

Verification statements describe the retained edition and its recorded evidence. This HTML presentation adds no Lean execution or proof review.

Start reading

Resources & source

Original TeX with line links · Download TeX

The wording and mathematics follow the retained manuscript. This reading format does not add a proof review or extend Lean coverage.

Skip contents and start reading

From the cut to a numerical lower bound

EXISTENCE, BALANCE, AND COMPLETE COVERAGE Write \(c=p\mathbin{++}q\). At this cut, Block 01 defines

\[ H_i(x)=\operatorname{run}(p)(x,0^a,0)_i{\mathbin{\oplus}} \operatorname{run}(q^{-1})(x,0^a,0)_i \]

and proves

\[ H_i\le f,\qquad f(x)=1\iff\exists i\;H_i(x)=1. \]

Reversal does not change Toffoli count. The new coordinate degree theorem therefore gives

\[ \deg(H_i)\le\max\{{\operatorname{tc}}(p),{\operatorname{tc}}(q)\}+1. \]

The least safe degree exists

For a positive \(v\), take the point indicator

\[ \delta_v(x)=\prod_{i=1}^{n} \begin{cases} x_i,&v_i=1,\\ 1+x_i,&v_i=0. \end{cases} \]

It is safe, detects \(v\), and has a degree-\(n\) certificate. Hence complete safe coverage exists at degree \(n\) for every function. Strong induction proves the existence of a least admissible natural degree. The definition beta chooses this bound and its specification and minimality are proved.

The balanced cut is constructed

Because each gate has cost zero or one, a prefix can realize every Toffoli count from zero to \(T\). The source proves this fact and extracts a cut with

\[ \max\{{\operatorname{tc}}(p),{\operatorname{tc}}(q)\}\le\left\lceil T/2\right\rceil. \]

The complete safe cut cover then proves

\[ \beta(f)\le\left\lceil T/2\right\rceil+1, \qquad\boxed{2\beta(f)\le T+3.} \]

Natural-number arithmetic retains the floor/ceiling and small-\(T\) cases. No balance assumption is added to the final theorem.

Source and conversion record

Source SHA-256: 36eb83548efd74b42264ab400e359c2de20c701b436b132b8b2859312d2dcdba

Unsupported prose commands stop the build. The mathematical expression sequence is checked against the source, with manuscript macros expanded for display.

Conversion records

Notation in Quantum and Circuits

Look up a symbol without leaving this chapter. Select text before opening help to search for it.

Search this work’s notation.

    Symbols can have different meanings in different passages. Read each result in its own context.

    Open the full notation index