Friday, July 26, 2013

Kalamidas Refuted

The three refuters of Demetrios Kalamidas
Recently Demetrios Kalamidas proposed a clever Bob-to-Alice FTL communication scheme involving a pair of path-entangled photons that passed peer review and was published in an esteemed American optics journal.

DK's scheme involved erasing Bob's which-path information by adding a number-uncertain (weak coherent) state to Bob's paths that produced an essential ambiguity as to which path the photon took. Kalamidas claimed that when this ambiguity was present at Bob's detectors, interference fringes would appear at Alice's distant detectors, without the need for a coincidence signal triggered by Bob's detector outputs. Kalamidas's scheme was not exact but involved two plausible approximations.

Several kinds of refutation were mounted to challenge the Kalamidas claim. Nick Herbert constructed a Kalamidas-inspired ambiguation scheme (2 MB pdf) involving Gray Light (x|0> + y|1>) instead of coherent states |A> which involved NO APPROXIMATIONS. Simple calculation of the EXACT Gray-Light scheme produced no FTL signals.

A different refutation by GianCarlo Ghirardi showed that if all photon operations are unitary, then an EXACT calculation shows that no FTL signaling is possible. However Ghirardi's proof is quite general and does not come to grips with the actual details of the Kalamidas scheme.

Next John Howell at University of Rochester examined a version of the Kalamidas scheme that involves adding a coherent state |A> to a single-photon Fock state |1> to create a displaced Fock state (DFS). Howell showed that an EXACT calculation of this DFS scheme leads to no FTL signaling.

However, Kalamidas's proposal is subtly different from the scheme that Howell refuted. Kalamidas's proposal adds the Fock state |1> and coherent state |A> in reverse order from Howell to produce a photon-added coherent state (PACS) rather than a DFS. Because these operations (photon addition) and (coherent state addition) do not commute, the PACS state is not the same as a DFS state.

So now a question arises: what is the correct output state (DFS or PACS) that emerges from a beam splitter when a coherent state |A> enters at one port and a Fock state |1> enters at the other?

This question was answered by Martin Suda at Austrian Institute of Technology who showed that BOTH OUTPUTS ARE CORRECT. The output of a beam splitter can be correctly described as an entanglement of DFS or of PACS states--a result I have dubbed the Martin Suda Equality. Even tho the relevant Boson operators do not commute, the Stokes relation for beam splitters "magically cancels" out the commutator and leads to this remarkable result.

So Kalamidas is correct in using PACS in his FTL proposal and Howell is also correct in using DCS in his disproof. Kalamidas uses an approximate PACS scheme; Howell's refutation uses an EXACT DCS scheme. Not yet a perfect match between proposal and refutation.

Then Christopher Gerry of Lehman College, CUNY, enters the fray with an EXACT refutation based on PACS states, concluding that "Clearly, if the exact calculation shows no interference, but the approximate calculation does, there is something wrong with the approximate calculation."

That would seem to have settled the matter, Gerry's calculation uses the same PACS states as Kalamidas and shows no FTL signaling. But, at least in my mind, one stumbling block remained: if Kalamidas's approximate calculation is wrong, then where is his mistake? Many of us have searched for this mistake (including myself, Howell, Suda and Gerry) without success.

Now I believe I have found it--not a mistake, but a way of looking at the Kalamidas proposal that exposes its crucial flaw.

Suppose (since none of us can refute it), that Kalamidas's calculation is correct. He has found an approximation scheme that yields true FTL signaling. What this means is that, if you coincidence-trigger on all Bob's terms of the Kalamidas approximation, you will generate interference in Alice's detectors.

But, even assuming Kalamidas's calculation is correct, he still loses the game, because for his scheme to work (since it is only approximate) it necessarily requires coincidence triggering. Because we know from the results of Ghirardi, Howell and Gerry, that the EXACT calculations show no sign of FTL signaling.

Therefore, using his own criterion (no coincidence triggering), the Kalamidas scheme must fail.

Besides the excitement generated by his clever new FTL signaling scheme, and a renewed excuse to delve into the details of Boson calculus, the most notable outcome of the Kalamidas affair seems to have been the discovery of the surprising "Martin Suda Equality".

Wednesday, July 3, 2013

Three by Kenneth Patchen

Who are you

Who are you
Watching out of the water lily
Watching out of the oak tree
Daughter of the linnet's waking
Draughtsman of the tempest's oath
Who are you
Watching out of the wounded fawn
Watching out of the frolicking hare
O designer of what awesome tidings

Alan Ginsberg & Kenneth Patchen

The artist's duty

So it is the duty of the artist to discourage 

all traces of shame

To extend all boundaries

To fog them in right over the plate

To kill only what is ridiculous

To establish problems

To ignore solutions

To listen to no one

To omit nothing

To contradict everything

To generate the free brain

To bear no cross

To take part in no crucifixion

To tinkle a warning when mankind strays

To explode upon all parties

To wound deeper than the soldier

To heal this poor obstinate monkey 
once and for all

To verify the irrational

To exaggerate all things

To inhabit everyone

To lubricate each proportion

To experience only experience

To set a flame in the high air

To expose himself to every ridicule
To have kids with pretty angels
To display his dancing seed

To exclaim at the commonplace alone

To cause the unseen eyes to open

To admire only the absurd

To be concerned with every profession 
save his own

To raise a fortuitous stink 
on the boulevards of truth and beauty

To desire an electrifiable intercourse 
with a female alligator

To lift the flesh above the suffering

To forgive the beautiful its disconsolate deceit

To flash his vengeful badge at every abyss


It is the artist’s duty to be alive

To drag people into glittering occupations

To blush perpetually in gaping innocence

To drift happily 
through the ruined race-intelligence

To burrow beneath the subconscious

To defend the unreal at the cost of his reason

To obey each outrageous impulse

To commit his company to all enchantments. 

Booker Ervin & Kenneth Patchen

The sea is awash with roses

The sea is awash with roses O they blow
Upon the land

The still hills fill with their scent
O the hills flow on their sweetness
As on God's hand

O love, it is so little we know of pleasure
Pleasure that lasts as the snow

But the sea is awash with roses O they blow
Upon the land