(For educational purposes only) This presentation is a partial fulfillment of our course Quantum Mechanics in MSU-IIT. This is a summary of the Christopher Monroe's Journal: What quantum computers may tell us about quantum mechanics. It is such a wonderful journal as it discusses the physics behind quantum computers and could help in building the foundation of quantum computers.

1. What quantum computers may tell
us about quantum mechanics
by Christopher R. Monroe
Presentation by: Maria Jane S. Poncardas
MSU-IIT
May 16, 2016
2:00 PM, CSM-130

2. What quantum computers may tell
us about quantum mechanics
•Quantum Information processing
•Quantum entanglement
•Quantum Computer Hardware

3. Introduction
• Quantum Mechanics foundations are often questioned
due to the difficulty of reconciling it with
classical laws of physics.
• Today’s technology leads to
the device being miniature
towards atomic scale.
• BUT:
• There will be unnecessary
QUANTUM TUNNELING of
electrons and large signal
fluctuations

4. First transistor created
at A&T’s Bell Labs on
December, 1947
First single-electron
transistor made entirely
of oxide-based
materials, 2011

5. •These miniaturization arises
quantum information processing
 faster devices in terms of its
performance
 eclipse the existing technology
--- instead of shrinking, we take advantage
of the principle

6. Quantum
Mechanics
Information
Theory
20th Century
Quantum Information Science
21st Century
QUANTUM INFORMATION PROCESSING

7. QUANTUM INFORMATION PROCESSING
• Began from discovery of binary
digits or bits by Claude Shannon.
Claude Shannon
• growth in the technology
of processing information
speed and computing power
is described
exponentially.

8. • Chip components also shrink in size
as described in Moore’s law.
Recall: Transistor is a device that regulates current or voltage flow and acts as a switch.

9. QUANTUM INFORMATION PROCESSING
• New information arise then as
the limit of classical bits are
met, such as quantum information
processing.
• Quantum bits – simplest
mechanical unit of information
can store superposition of 0 and
1.
Ψ = α 0 > + β 1 >
where α and β are complex
amplitudes of superposition.

10. QUANTUM INFORMATION PROCESSING
• for N qubits, it stores a
superposition of 2N binary numbers.
• 2N are possibilities of measurement*
• The trick behind a useful quantum
computer is the phenomenon called
quantum interference.
--- *complex amplitude interfering
to cancel out leaving only few or
one answer.*

11. QUANTUM ENTANGLEMENT
• It is the combination
of two properties in QM
– superposition and
measurement.*
• It is the most
misunderstood concept in
quantum mechanics.

12. QUANTUM ENTANGLEMENT
• Definition 1:
An entangled state is one that is not
separable, where measurements are
performed on one constituent without
affecting the others.
• There is a correlation between subsystems and
entangled state*
• High detector quantum efficiency is needed

13. QUANTUM ENTANGLEMENT
• Definition 2:
An entangled state is one that is not
separable, where highly quantum-
efficient measurements are performed
on one constituent without affecting
the others, and where the constituents
are spacelike separated during the
measurement time.
• Have considered Bell’s inequality
• Requiring space-like separation

14. QUANTUM COMPUTER HARDWARE
• The definition of quantum
entanglement comprise the reference
in building a quantum computer.
i.
ii.
Arbitrary unitary operators must be available and
controlled to launch an initial state to an arbitrary
entangled state
Measurements of the qubits must be performed with
high quantum efficiency.

15. QUANTUM COMPUTER HARDWARE
• Physicists are in search for
quantum measurement.
• Theories like Bohmian mechanics,
many-worlds interpretations,
transactional interpretation and the
quantum decoherence theory, does not
address the quantum measurement
problems.

16. QUANTUM COMPUTER HARDWARE
• There at least one alternative:
“spontaneous wave function collapse”
--the observer collapsed the wave function by
simply observing.
• attempts to meld quantum measurement
and QM by adding nonlinear stochastic
driving field to quantum mechanics
that randomly localizes or collapses
the wave function

17. OUTLOOK
This journey towards quantum computers
yields at least three possible results:
o a full-blown large-scale quantum
computer will be built
o theory of quantum mechanics will be
found incomplete
o we can never reach the first
possibility due to economic
constraints.

18. References:
• https://www.ias.edu/ideas/2014/ambainis-quantum-computing
• http://www.chemistryviews.org/details/news/1054617/Worlds_Smalles
t_Transistor.html
• Source: http://www.extremetech.com/extreme/175004-the-genesis-of-
the-transistor-the-single-greatest-discovery-in-the-last-100-
years
• http://history-computer.com/ModernComputer/thinkers/Shannon.html
• https://www.elektormagazine.com/articles/moores-law
• https://www.youtube.com/watch?v=aWLBmapcJRU
• http://www.daviddarling.info/encyclopedia/Q/quantum_entanglement.
html
• http://qoqms.phys.strath.ac.uk/research_qc.html
• https://www.engineering.unsw.edu.au/news/quantum-computing-first-
two-qubit-logic-gate-in-silicon

19. • https://en.wikipedia.org/wiki/Bell's_theorem#Original_Bell.27s_inequality
• https://uwaterloo.ca/institute-for-quantum-computing/quantum-computing-
101#Superposition-and-entanglement
• https://en.wikipedia.org/wiki/Double-slit_experiment