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Complementarity of resources:. work, entanglement, reference. quant-ph/0501121. John Vaccaro Howard Wiseman Kurt Jacobs. Fabio Anselmi. University of Hertfordshire Hatfield, UK. Griffith University Brisbane, Australia. S. This talk. Superselection Rules (SSRs) - PowerPoint PPT Presentation
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1U HMilano 05
Fabio AnselmiFabio Anselmi
University of Hertfordshire Hatfield, UK
John VaccaroJohn VaccaroHoward WisemanHoward WisemanKurt JacobsKurt Jacobs
Griffith University Brisbane, Australia
quant-ph/0501121
2U HMilano 05
W
GGA
)(loGGW
GGE
This talkThis talk•Superselection Rules (SSRs)
– conservation of local particle number– general symmetry groups
•Reference frames– asymmetry: ability to act as a reference
•Extracting mechanical work•Bipartite systems under SSR•Accessible entanglement•Extracting local work•Hierarchy of restrictions/resources• Complementarity
S
g
h
3U HMilano 05
Superselection RulesSuperselection Rules
all physical operations conserve particle number
cannot observe coherence between subspaces of different particle number
effectively a superselection rule.
n
1n
2n
1n
1n
ie
Conservation of particle number
4U HMilano 05
Symmetry group: }{gG unitary representation: GggT )(
Operationally accessible states
N
dee NiNi
ˆ
2ˆ)ˆ(
2
ˆˆ
G
Expressed as symmetry group U(1)
General symmetry group
Operationally accessible states
Gg
gTgTG
)(ˆ)(][
1ˆ 1G
projective measurement of
Ssystem under SO(2)
} { ˆ NieG
reduced coherence
S
“crisp“
5U HMilano 05
Reference systems (frames)Reference systems (frames)
Measure of asymmetry ˆˆ)ˆ( SSAG G
Reference frames break the symmetry preserve coherence of system
R
reference system
asymmetric system
S
von Neumann entropy induced by G
Any system with asymmetry can act as a reference system (frame) for G
A symmetric system cannot act as a reference.
Gg
gTgTG
)(ˆ)(][
1ˆ 1G
6U HMilano 05
iff is symmetric:
0)ˆ( GA
Properties of asymmetry
0)ˆ( GA ˆˆ G)ˆ(GA does not increase for G-SSR operations Q
GggTgTgTgT )(]ˆ[)()](ˆ)([ 11 QQ
Synergy of is given by)ˆ(GW)]ˆ()ˆ([)ˆˆ()ˆ,ˆ,( 212121 GGGG WWWW
})ˆ(),ˆ(min{ 21 GG AA
ˆˆ)ˆ( SSAG G
Gg
gTgTG
)(ˆ)(][
1ˆ 1Gi)
ii)
iii)
iv)
7U HMilano 05
Example of Abelian case (particle number)
N
n
inNR
ne0
11)(
10 S
N
n
iinNRS
nene1
11 110)(
-invariant to -coherence is preserved
22
222
2 loglog11 N
Niegˆ
)(
Nie ˆ
22
222
2 loglog)( SGA
system:
asymmetry
reference:
)1(log)( 2 NA RG asymmetry
reduction in asymmetry (synergy):
R S
combined:
Pegg & Barnett (1989).
8U HMilano 05
Example of Abelian case (particle number)
N
n
inNR
ne0
11)(
10 S
N
n
iinNRS
nene1
11 110)(
-invariant to -coherence is preserved
22
222
2 loglog11 N
Niegˆ
)(
Nie ˆ
22
222
2 loglog)( SGA
system:
asymmetry
reference:
)1(log)( 2 NA RG asymmetry
reduction in asymmetry (synergy):
R S
combined:
Pegg & Barnett (1989).
9U HMilano 05
Extracting mechanical workExtracting mechanical work
)]ˆ([log)ˆ( SDTkW B
)ˆ(log)ˆ( SDW
1
under SSR)ˆ(log)ˆ( GSDWG
10U HMilano 05
)ˆ(log)ˆ( GSDWG
)ˆ(log)ˆ( SDW
)ˆ()ˆ()ˆ( SSAG G)ˆ()ˆ()ˆ( GG AWW
GA
)ˆ(W
resource?
GW
11U HMilano 05
acting separately
acting as single system
Upper bound
asymmetry is a resource
S R
gG fG
advantage of acting as a composite system
Synergy
R S
gG
)]ˆ()ˆ([)ˆˆ()ˆ,ˆ,( SGRGSRGSRG WWWW
)ˆ( )}ˆ(),ˆ(min{)ˆ,ˆ,(
RG
SGRGSRG
AAAW
12U HMilano 05
Bipartite systems under SSRBipartite systems under SSR
)ˆ]([)ˆ( BAGG WW GG
Ghg
BA hTgThTgTG ,
11 )]()([ˆ)]()([][
1ˆ][ GG
Local action of the group: local G-SSR
][ BA GG g
h
13U HMilano 05
iff is locally symmetric:
0)ˆ( GGA
Local asymmetry
0)ˆ( GGA ˆˆ]1[ˆ]1[ BABA GG
)ˆ(GGA does not increase for locally G-SSR operations QSynergy of is given by)ˆ(GGW
)]ˆ()ˆ([)ˆˆ()ˆ,ˆ,( 212121 GGGGGGGG WWWW
})ˆ(),ˆ(min{ 21 GGGG AA
ˆˆ][)ˆ( SSA BAGG GG
i)
ii)
iii)
iv)
)ˆ()ˆ()ˆ( GGGG AWW
)ˆ(GGW
GGA
)ˆ(W
can act as local & sharedreference
GGW
g
h
14U HMilano 05
fixed total number of N particles
N
nnNnnf
0,
+ +
N
n N-n
Accessible entanglement under SSRAccessible entanglement under SSR
f n
nNnE ,
A B
nNn
N
nnGG EfE
,
0
2
Wiseman and Vaccaro, PRL 91, 097902 (2003).
17
6 11
EE GG
15U HMilano 05
Super-additivity:
01001 GGE
-releases “latent” entanglement-a kind of distillation
cross terms represent 1 particle at each site – no particle entropy
A B
A B
1,1
2,0
0,2
+
Examples
GGGGGG EEE
16U HMilano 05
Extracting Extracting locallocal work work Oppenheim et al PRL 89, 180402 (2002)
)ˆ()( loW
)ˆ()( loW
17U HMilano 05
)()(, ˆˆˆ B
jA
ijic QQ
LOC
C
local extraction of work)ˆ()ˆ()( QWW lo
classically-correlated state with min entropy
equivalent method
classical channel
18U HMilano 05
classical channel
)()(, ˆˆˆ B
jA
ijic QQ
LOC
C
local extraction of work)ˆ()ˆ()ˆ()( EWW lo
classically-correlated state with min entropy
pure state
dephase in Schmidt basis
equivalent method for pure states
)ˆ()ˆ()ˆ( )( EWW lo
19U HMilano 05
Extracting Extracting locallocal work under local SSR work under local SSR )ˆ()( loGGW
)ˆ()( loGGW
][ BA GG g
h
20U HMilano 05
classical channel
ˆˆ GFor pure, globally-symmetric states
)()(, ˆˆˆ B
jA
ijic QQ
LOC
C
local extraction of work)ˆ()ˆ()ˆ()ˆ()( GGGG
loGG AEWW
classically-correlated state with min entropy
dephase in Schmidt basis
][ BA GG g
h
)ˆ()ˆ()ˆ()ˆ( )( GGGGlo
GG AEWW
21U HMilano 05
work
local symmetry
local asymmetry
)ˆ()ˆ()ˆ()ˆ( )( GGGGlo
GG AEWW
W
GGlo
GG EW )( GGA
can act as a local reference
22U HMilano 05
mechanical
logical
local asymmetry
can act as a local reference
)ˆ()ˆ()ˆ()ˆ( )( GGGGlo
GG AEWW
W
GGA
)(loGGW
GGE
local symmetry
23U HMilano 05
A B
A B
0110
S R
R
ability to act as shared reference
super-additivity of accessible entanglement=
01100110
1 0 1 2
)(
GGGG
loGG AEWW
1 1 2
)(
EWW lo
23
21
)(
2 4
GGGGlo
GG AEWW
2 2 4
)(
EWW lo
GGA
Recall examples for U(1)
24U HMilano 05
A B
A B
0110
S R
R
ability to act as shared reference
super-additivity of accessible entanglement=
01100110
1 0 1 2
)(
GGGG
loGG AEWW
1 1 2
)(
EWW lo
23
21
)(
2 4
GGGGlo
GG AEWW
2 2 4
)(
EWW lo
GGA
Recall examples for U(1)LOCC LOCC+LocalG
25U HMilano 05
Symmetry group: }{gG Unitary representation: GggT )(
Locally accessible states
Details of general group caseDetails of general group case
Gg
gTgTG
)(ˆ)(][
1)ˆ( 1G Globally-symmetric states
ˆˆ G
Ghg
BA hTgThTgTG ,
11 )]()([ˆ)]()([][
1ˆ][ GG
26U HMilano 05
Elemental globally symmetric state
,
,, ,
, mmmm
mmd
)()()( , gTgTgT
where and are conjugate w.r.t. :
,,
,, )()( mmmm ggT
i.e.:
General globally symmetric state
ji
jimm jmim
DC
,
,,, ,,,,
multiplicity “flavour”
1 dim irrep
“charge”
“colour”
27U HMilano 05
PPdEPE mmGG 2, log)(
,
,, ,
, mmmm
mmd
entanglement due to multiplicity indices mm ,
reduced by entropy associated with
DPPPA GG
1log2log 22
ji
jimm jmim
DC
,
,,, ,,,,
entropy associated with mixing of i & j indices
entropy associated with charge fluctuations
28U HMilano 05
W
ability to act as a reference frame
RFW
asymmetry
Complementarity of resourcesComplementarity of resources
symmetry
asymsym
)ˆ()ˆ()ˆ()ˆ( )( GGGGlo
GG AEWW
)(loGGW
GGE
M L
GGA
ability to perform work
29U HMilano 05
Hierarchy of Hierarchy of restrictions-resourcesrestrictions-resources
GG AWW
GGGG AWW
GGGGlo
GG AEWW )(
EWW lo )(LOCC
G
GG
LOCC, GG
WW -
for globally-symmetric states
g
h
g
h
30U HMilano 05
• reference frames
• accessible entanglement and work
• complementarity of resources: reference ability
versus mechanical work
versus logical work
SummarySummary
R
reference f rame
asymmetric system
S
1,1
2,0
0,2
+
W
GGA
)(loGGW
GGE
triality
31U HMilano 05
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