2. The memory capacity of a chip approximately doubles every
18 months – clock speeds and transistor density are rising
exponentially...what is their ultimate fate????
Real computers are physical systems
Computer technology in the last fifty years-
dramatic miniaturization
Faster and smaller –
4. Extrapolating Moore’s law
• If Moore’s law is extrapolated, by the year
2020 the basic memory component of the
chip would be of the size of an atom – what
will be space, time and energy
considerations at these scales (heat
dissipation…)?
• At such scales, the laws of quantum physics
would come into play - the laws of quantum
physics are very different from the laws of
classical physics - everything would change!
5. Bra-Ket Notation Involves
Vector Xn can be represented two
ways
Ket
|n>
z
y
x
w
v
Bra
<n| = |n>t
( )*****
zyxwv
*
m is the complex conjugate of m.
7. Classical Circuits
vs.
Quantum Circuits
Classical Circuits based upon bits, which are
represented with on and off states. These states
are usually alternatively represented by 1 and 0
respectively.
The medium of transportation of a bit is a
conductive material, usually a copper wire or
something similar. The 1 or 0 is represented with
2 different levels of current through the wire.
8. Circuits Continued…
Quantum circuits use electron “spin” to hold
their information, instead of the conductor
that a classical circuit uses.
While a classical circuit uses transistors to
perform logic, quantum circuits use
“quantum gates” such as the Hadamard
Gates.
11. Hadamard Gates
Hadamard Gates can perform logic and are
usually used to initialize states and to add
random information to a circuit.
Hadamard Gates are represented
mathematically by the Hadamard Matrix which
is below.
−
=
11
11
2
1
H
12. Circuit Diagram of a
Hadamard Gate
Hx y
When represented in a Quantum Circuit
Diagram, a Hadamard Gate looks like this:
Where the x is the input qubit and the y is
the output qubit.
13. C-Not Gates
C-not Gates are one of the basic 2-qubit gates in
quantum computing. C-not is short for controlled
not, which means that one qubit (target qubit) is
flipped if the other qubit (control qubit) is |1>,
otherwise the target qubit is left alone.
The mathematical representation of a C-Not Gate
is below.
=
0100
1000
0010
0001
CNU
14. Circuit Diagram of a C-Not Gate
x
y
x
yx ⊕
When represented in a Quantum Circuit
Diagram, a C-Not Gate looks like this:
Where x is the control qubit and y is the
target qubit.