Picturing Quantum Processes Aleks Kissinger QTFT, V axj o 2015 - - PowerPoint PPT Presentation

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Picturing Quantum Processes Aleks Kissinger QTFT, V axj o 2015 - - PowerPoint PPT Presentation

Introduction 1. Linear maps 2. Quantum maps 3. Consequences 4. Classical 5. Complementarity Picturing Quantum Processes Aleks Kissinger QTFT, V axj o 2015 June 10, 2015 Introduction 1. Linear maps 2. Quantum maps 3. Consequences


slide-1
SLIDE 1

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Picturing Quantum Processes

Aleks Kissinger

QTFT, V¨ axj¨

  • 2015

June 10, 2015

slide-2
SLIDE 2

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum Picturalism: what it is, what it isn’t

  • ‘QPism’ ☺ is a methodology for expressing, teaching, and reasoning

about quantum processes

slide-3
SLIDE 3

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum Picturalism: what it is, what it isn’t

  • ‘QPism’ ☺ is a methodology for expressing, teaching, and reasoning

about quantum processes

  • Diagrams live at the centre, thus composition and interaction
slide-4
SLIDE 4

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum Picturalism: what it is, what it isn’t

  • ‘QPism’ ☺ is a methodology for expressing, teaching, and reasoning

about quantum processes

  • Diagrams live at the centre, thus composition and interaction
  • QP is not a reconstruction, but some ideas from operational reconstructions

play a major role, e.g.

ρ′ µ ρ ρ Φ ρ′

local/process tomography

Φ =

  • f

purification

slide-5
SLIDE 5

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum Picturalism: what it is, what it isn’t

  • ‘QPism’ ☺ is a methodology for expressing, teaching, and reasoning

about quantum processes

  • Diagrams live at the centre, thus composition and interaction
  • QP is not a reconstruction, but some ideas from operational reconstructions

play a major role, e.g.

ρ′ µ ρ ρ Φ ρ′

local/process tomography

Φ =

  • f

purification

  • ...and relationship between operational setups and theoretical models:
  • =

ρ

  • U
  • U
slide-6
SLIDE 6

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Picturing Quantum Processes

A first course in quantum theory and diagrammatic reasoning Bob Coecke & Aleks Kissinger CUP 2015

slide-7
SLIDE 7

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

slide-8
SLIDE 8

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

  • 1. Process theory of linear maps
slide-9
SLIDE 9

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

  • 1. Process theory of linear maps
  • 2. quantum maps via ‘doubling’ construction
slide-10
SLIDE 10

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

  • 1. Process theory of linear maps
  • 2. quantum maps via ‘doubling’ construction
  • 3. Consequences: purification, causality, no-signalling, no-broadcasting
slide-11
SLIDE 11

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

  • 1. Process theory of linear maps
  • 2. quantum maps via ‘doubling’ construction
  • 3. Consequences: purification, causality, no-signalling, no-broadcasting
  • 4. Classical/quantum interaction
slide-12
SLIDE 12

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Outline

Picturing Quantum Processes chapters 4-9 (roughly)

  • 1. Process theory of linear maps
  • 2. quantum maps via ‘doubling’ construction
  • 3. Consequences: purification, causality, no-signalling, no-broadcasting
  • 4. Classical/quantum interaction
  • 5. Complementarity
slide-13
SLIDE 13

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Recap

  • Wires represent systems, boxes represent processes

quicksort

lists lists

cooking

bacon breakfast eggs food

baby

love poo noise

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SLIDE 14

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Recap

  • Wires represent systems, boxes represent processes

quicksort

lists lists

cooking

bacon breakfast eggs food

baby

love poo noise

  • The world is organised into process theories, collections of processes that

make sense to combine into diagrams

g

A

ψ

h

B C A D A

processes systems

slide-15
SLIDE 15

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Recap

  • Certain processes play a special role:

states: ψ effects: φ numbers:

λ

slide-16
SLIDE 16

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Recap

  • Certain processes play a special role:

states: ψ effects: φ numbers:

λ

  • State + effect = number, interpreted as:

ψ φ test state probability

this is called the Born rule.

slide-17
SLIDE 17

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

linear maps

In the process theory of linear maps:

slide-18
SLIDE 18

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

linear maps

In the process theory of linear maps: (L1) Every type has a (finite) basis:    for all i : i f = i g     = ⇒ f = g

slide-19
SLIDE 19

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

linear maps

In the process theory of linear maps: (L1) Every type has a (finite) basis:    for all i : i f = i g     = ⇒ f = g (L2) Processes can be summed:

  • i

fi where

  • i
  • f

hi g g =

  • i

            f g hi g            

slide-20
SLIDE 20

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

linear maps

In the process theory of linear maps: (L1) Every type has a (finite) basis:    for all i : i f = i g     = ⇒ f = g (L2) Processes can be summed:

  • i

fi where

  • i
  • f

hi g g =

  • i

            f g hi g            

(L3) Numbers are the complex numbers:

λ

∈ C

slide-21
SLIDE 21

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

slide-22
SLIDE 22

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

Proof.

i f j = i g j

slide-23
SLIDE 23

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

Proof.

f j = g j

slide-24
SLIDE 24

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

Proof.

j f = j g

slide-25
SLIDE 25

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

Proof.

f = g

slide-26
SLIDE 26

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

Proof.

f = g

slide-27
SLIDE 27

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bases ⇔ process tomography

Theorem

      for all i , j : i f j = i g j       = ⇒ f = g

  • In other words, f is uniquely fixed by its matrix:

       f 1

1

f 1

2

· · · f 1

m

f 2

1

f 2

2

· · · f 2

m

. . . . . . ... . . . f n

1

f n

2

· · · f n

m

       where f j

i

:= i f j

slide-28
SLIDE 28

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What about the Born rule?

ψ φ test state probability

slide-29
SLIDE 29

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

The Born rule for relations

ψ φ test state B := {0, 1}

slide-30
SLIDE 30

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

The Born rule for relations

ψ φ test state B := {0, 1} possibility

slide-31
SLIDE 31

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

The Born rule for linear maps

ψ φ test state C ???

slide-32
SLIDE 32

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Fixing the problem

ψ φ test state R≥0 probability ψ φ

slide-33
SLIDE 33

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Doubled states and effects

Letting: ψ ψ :=

  • ψ

and φ φ :=

  • φ
slide-34
SLIDE 34

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Doubled states and effects

Letting: ψ ψ :=

  • ψ

and φ φ :=

  • φ

yields... test state probability ψ ψ φ φ := :=

  • ψ
  • φ
slide-35
SLIDE 35

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

A new process theory from an old one...

  • The theory of pure quantum maps has types:

:=

  • A
slide-36
SLIDE 36

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

A new process theory from an old one...

  • The theory of pure quantum maps has types:

:=

  • A
  • and processes:

=

  • f

f f for all processes f from linear maps.

slide-37
SLIDE 37

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Embedding the old theory

  • linear maps embed in quantum maps, and this embedding preserves

diagrams: double         f g h         =

  • g
  • h
  • f
slide-38
SLIDE 38

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Embedding the old theory

  • linear maps embed in quantum maps, and this embedding preserves

diagrams: double         f g h         =

  • g
  • h
  • f
  • But now we’re in a bigger space, so there is room for something new
slide-39
SLIDE 39

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Embedding the old theory

  • linear maps embed in quantum maps, and this embedding preserves

diagrams: double         f g h         =

  • g
  • h
  • f
  • But now we’re in a bigger space, so there is room for something new,

discarding:

  • ψ

=

slide-40
SLIDE 40

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ ???

slide-41
SLIDE 41

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ

slide-42
SLIDE 42

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ = ψ ψ =

slide-43
SLIDE 43

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ = ψ ψ =

  • So discarding is defined as the effect:

:=

slide-44
SLIDE 44

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ = ψ ψ =

  • So discarding is defined as the effect:

:=

  • In fact, this is the unique map with this property. Let {

ψi}i be a basis of pure states (e.g. z+, z−, x+, y+), then:

  • ψi

= d

  • ψi

=

slide-45
SLIDE 45

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

What is discarding?

  • ψ

= ψ ψ = ψ ψ =

  • So discarding is defined as the effect:

:=

  • In fact, this is the unique map with this property. Let {

ψi}i be a basis of pure states (e.g. z+, z−, x+, y+), then:

  • ψi

= d

  • ψi

= = ⇒ = d

slide-46
SLIDE 46

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

quantum maps

Definition

The process theory of quantum maps consists of all processes obtained from pure quantum maps and discarding:

  • f

. . .

  • . . .
slide-47
SLIDE 47

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

quantum maps

Definition

The process theory of quantum maps consists of all processes obtained from pure quantum maps and discarding:

  • f

. . .

  • . . .
  • e.g.

ρ :=

  • ψ

and Φ :=

  • f
  • g
  • h
slide-48
SLIDE 48

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
slide-49
SLIDE 49

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
  • To get all of the deterministically realisable processes, we additionally

require causality: Φ =

slide-50
SLIDE 50

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
  • To get all of the deterministically realisable processes, we additionally

require causality: Φ =

  • Causality =

⇒ no-signalling: Ψ Φ ρ Alice Bob

slide-51
SLIDE 51

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
  • To get all of the deterministically realisable processes, we additionally

require causality: Φ =

  • Causality =

⇒ no-signalling: Ψ Φ ρ Alice Bob

slide-52
SLIDE 52

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
  • To get all of the deterministically realisable processes, we additionally

require causality: Φ =

  • Causality =

⇒ no-signalling: Ψ Φ ρ Alice Bob = Bob Ψ Alice ρ

slide-53
SLIDE 53

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Causality

  • This gives all quantum processes, including post-selected ones
  • To get all of the deterministically realisable processes, we additionally

require causality: Φ =

  • Causality =

⇒ no-signalling: Ψ Φ ρ Alice Bob = Bob Ψ Alice ρ Alice = Ψ′ Bob

slide-54
SLIDE 54

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Purification

  • Any quantum map extends to a pure quantum map on an extended system:

Φ =

  • f
slide-55
SLIDE 55

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Purification

  • Any quantum map extends to a pure quantum map on an extended system:

Φ =

  • f
  • This is built-in to our definition of quantum maps:
  • f
  • g
  • h

  • g
  • f
  • h
slide-56
SLIDE 56

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Purification

  • Any quantum map extends to a pure quantum map on an extended system:

Φ =

  • f
  • This is built-in to our definition of quantum maps:
  • f
  • g
  • h

  • g
  • f
  • h
  • If Ψ causal,

f must be isometry: Stinespring dilation.

slide-57
SLIDE 57

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension

Theorem

A state is pure if and only if any extension separates:

  • ψ

= ρ = ⇒ ρ =

  • ψ

ρ′

slide-58
SLIDE 58

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension

Theorem

A state is pure if and only if any extension separates:

  • ψ

= ρ = ⇒ ρ =

  • ψ

ρ′

Corollary

There exists no quantum map ∆ such that: ∆ = ∆ =

slide-59
SLIDE 59

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension - proof

Broadcast to the left: = ∆

slide-60
SLIDE 60

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension - proof

Broadcast to the left: = ∆ Bend the wire: ∆ =

slide-61
SLIDE 61

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension - proof

Broadcast to the left: = ∆ Bend the wire: ∆ = = ⇒ ∆ = ρ

slide-62
SLIDE 62

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

No-broadcasting from pure extension - proof

Broadcast to the left: = ∆ Bend the wire: ∆ = = ⇒ ∆ = ρ Unbend the wire and try to broadcast to the right: ∆ = ρ = ⇒ ∆ = ρ

slide-63
SLIDE 63

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical systems

  • Protocols, experiments, etc. are always about the interaction of quantum

and classical systems

slide-64
SLIDE 64

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical systems

  • Protocols, experiments, etc. are always about the interaction of quantum

and classical systems

  • We extend graphical language:

quantum systems → double wires classical systems → single wires

slide-65
SLIDE 65

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical systems

  • Protocols, experiments, etc. are always about the interaction of quantum

and classical systems

  • We extend graphical language:

quantum systems → double wires classical systems → single wires

  • States are probability distributions:

p =

j

pj j ↔      p1 p2 . . . pn     

slide-66
SLIDE 66

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical systems

  • Protocols, experiments, etc. are always about the interaction of quantum

and classical systems

  • We extend graphical language:

quantum systems → double wires classical systems → single wires

  • States are probability distributions:

p =

j

pj j ↔      p1 p2 . . . pn     

  • Processes are stochastic maps:

f ↔        p1

1

p1

2

· · · p1

m

p2

1

p2

2

· · · p2

m

. . . . . . ... . . . pn

1

pn

2

· · · pn

m

      

slide-67
SLIDE 67

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical operations

  • Deleting is marginalisation:

:=

i

i

slide-68
SLIDE 68

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical operations

  • Deleting is marginalisation:

:=

i

i

  • Classical causality just means stochastic:

f =

slide-69
SLIDE 69

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Classical operations

  • Deleting is marginalisation:

:=

i

i

  • Classical causality just means stochastic:

f =

  • We can broadcast classically:

= = where :=

i

i i i

slide-70
SLIDE 70

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Generalising to spiders

  • These generalise to a whole family of maps, called spiders:

· · · · · · · · i i i i i i :=

n m

  • i

· · · · · · · ·

n m

slide-71
SLIDE 71

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Generalising to spiders

  • These generalise to a whole family of maps, called spiders:

· · · · · · · · i i i i i i :=

n m

  • i

· · · · · · · ·

n m

  • where the only rule to remember is:

... ...

...

= ... ... ... ...

slide-72
SLIDE 72

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum spiders

  • A quantum spider is a classical spider, doubled:

... ... := double

  • ...

...

  • =

... ...

slide-73
SLIDE 73

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum spiders

  • A quantum spider is a classical spider, doubled:

... ... := double

  • ...

...

  • =

... ...

  • An example is the GHZ state:

GHZ := = double

  • i

i i i

slide-74
SLIDE 74

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Quantum spiders

  • A quantum spider is a classical spider, doubled:

... ... := double

  • ...

...

  • =

... ...

  • An example is the GHZ state:

GHZ := = double

  • i

i i i

  • They also fuse:

... ... ... ...

...

= ... ...

slide-75
SLIDE 75

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bastard spiders

  • The third type of spider treats some legs as classical, and some pairs of legs

as quantum: ... ... ... ... ... ... ... ... :=

slide-76
SLIDE 76

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bastard spiders

  • The third type of spider treats some legs as classical, and some pairs of legs

as quantum: ... ... ... ... ... ... ... ... :=

  • We call these (seemingly) weird things bastard spiders
slide-77
SLIDE 77

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Bastard spiders

  • The third type of spider treats some legs as classical, and some pairs of legs

as quantum: ... ... ... ... ... ... ... ... :=

  • We call these (seemingly) weird things bastard spiders
  • Again they fuse together:

... ...

...

= ... ... ... ...

slide-78
SLIDE 78

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Measurement’s a bastard

  • The most important example is ONB-measurement:

:: ρ →      P(1|ρ) P(2|ρ) . . . P(n|ρ)     

slide-79
SLIDE 79

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Measurement’s a bastard

  • The most important example is ONB-measurement:

:: ρ →      P(1|ρ) P(2|ρ) . . . P(n|ρ)     

  • whose adjoint is ONB-encoding:

:: i → i

slide-80
SLIDE 80

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Measurement’s a bastard

  • The most important example is ONB-measurement:

:: ρ →      P(1|ρ) P(2|ρ) . . . P(n|ρ)     

  • whose adjoint is ONB-encoding:

:: i → i

  • Combining these yields more general stuff, e.g. non-demo measurements:

=

slide-81
SLIDE 81

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Multi-coloured spiders

  • Different bases → different coloured spiders

m

  • ...

...

n

:=

i m

  • i

· · · · · i i · · · i

  • n

m

  • · · ·

· · · · ·

  • n

:=

i m

  • i

· · · · · i i · · · i

  • n
slide-82
SLIDE 82

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Multi-coloured spiders

  • Different bases → different coloured spiders

m

  • ...

...

n

:=

i m

  • i

· · · · · i i · · · i

  • n

m

  • · · ·

· · · · ·

  • n

:=

i m

  • i

· · · · · i i · · · i

  • n
  • Two spiders

and are complementary if: = (encode in ) + (measure in ) = (no data transfer)

slide-83
SLIDE 83

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Complementarity – Stern-Gerlach

  • For example, we can model Stern-Gerlach:

N S

S N

S N

  • X

Z Z

slide-84
SLIDE 84

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Complementarity – Stern-Gerlach

  • For example, we can model Stern-Gerlach:

N S

S N

S N

  • X

Z Z

  • which simplifies as:

= =

no data transfer

slide-85
SLIDE 85

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

slide-86
SLIDE 86

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

  • 1. Quantum info: Complementarity and cousin strong complementary give

graphical presentations for many protocols, e.g. QKD, QSS

slide-87
SLIDE 87

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

  • 1. Quantum info: Complementarity and cousin strong complementary give

graphical presentations for many protocols, e.g. QKD, QSS

  • 2. Quantum computing: Complementary spiders give a handy toolkit for

building quantum circuits and MBQC

slide-88
SLIDE 88

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

  • 1. Quantum info: Complementarity and cousin strong complementary give

graphical presentations for many protocols, e.g. QKD, QSS

  • 2. Quantum computing: Complementary spiders give a handy toolkit for

building quantum circuits and MBQC

  • 3. Quantum resources: Framework for resource theories, e.g. entanglement,

purity

slide-89
SLIDE 89

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

  • 1. Quantum info: Complementarity and cousin strong complementary give

graphical presentations for many protocols, e.g. QKD, QSS

  • 2. Quantum computing: Complementary spiders give a handy toolkit for

building quantum circuits and MBQC

  • 3. Quantum resources: Framework for resource theories, e.g. entanglement,

purity

  • 4. Quantum foundations: (spoiler alert!) GHZ/Mermin argument in

diagrams

slide-90
SLIDE 90

Introduction

  • 1. Linear maps
  • 2. Quantum maps
  • 3. Consequences
  • 4. Classical
  • 5. Complementarity

Applications

Picturing Quantum Processes the rest...

  • 1. Quantum info: Complementarity and cousin strong complementary give

graphical presentations for many protocols, e.g. QKD, QSS

  • 2. Quantum computing: Complementary spiders give a handy toolkit for

building quantum circuits and MBQC

  • 3. Quantum resources: Framework for resource theories, e.g. entanglement,

purity

  • 4. Quantum foundations: (spoiler alert!) GHZ/Mermin argument in

diagrams

Thanks!