Quan­tum leap in ‘spooky ac­tion at a dis­tance’

China Daily (Hong Kong) - - COMMENT -

The dis­tin­guished Amer­i­can physi­cist Richard Feyn­man once said that if you think you un­der­stand quan­tum me­chan­ics, you don’t. The science be­hind the laws that gov­ern the sub-atomic world has evolved over more than a cen­tury, re­veal­ing that the small­est par­ti­cles be­have out­side the realm of clas­si­cal physics.

Physi­cists have had to con­front the weird re­al­ity that, at the small­est level, ob­jects can be­have as both par­ti­cles and waves and, even more bizarrely, can be de­scribed as be­ing in two places at once.

Even though the the­o­ries gov­ern­ing the sub-atomic world are still evolv­ing, giv­ing rise to al­ter­na­tive ex­pla­na­tions of the na­ture of the uni­verse — or, as some would con­tend, uni­verses — quan­tum me­chan­ics has al­ready pro­vided the ba­sis for tech­no­log­i­cal ad­vances in the mod­ern world.

Prac­ti­cal ap­pli­ca­tions of quan­tum the­ory in­clude su­per­con­duct­ing mag­nets, the laser beam, tran­sis­tors and the mi­cro­pro­ces­sors that are at the heart of mod­ern com­put­ing.

The next stage in this evo­lu­tion is the field of tele­trans­porta­tion, an even more science-fic­tion sound­ing con­cept in which minute ob­jects can be moved in­stantly across wide dis­tances.

Chi­nese sci­en­tists this month claimed a world dis­tance record with the an­nounce­ment that they had suc­cess­fully tele­ported a sub-atomic par­ti­cle from the Earth to an or­bit­ing satel­lite up to 1,400 kilo­me­ters away.

In its lat­est ex­per­i­ment, a Chi­nese team of sci­en­tists fired a laser from a ground sta­tion in the Ti­bet au­ton­o­mous re­gion to the or­bit­ing Mi­cius satel­lite. In so do­ing, the team ef­fec­tively tele­ported a pho­ton across space.

Quan­tum tele­por­ta­tion oc­curs when the prop­er­ties of one ob­ject are in­stantly trans­ferred to an­other at a dis­tance. The re­mote pho­ton takes on the iden­tity of the one from the Earth and, to all in­tents and pur­poses, be­comes the same ob­ject.

Al­bert Ein­stein called the phe­nom­e­non quan­tum en­tan­gle­ment or “spooky ac­tion at a dis­tance”.

The ex­per­i­ment raises fa­mil­iar science fic­tion im­ages of larger ob­jects and even hu­mans be­ing tele­ported through space, phys­i­cally beamed from one lo­ca­tion to an­other. That is likely to re­main in the realm of science fic­tion, at least for now. How­ever, sci­en­tists have al­ready seized on po­ten­tial prac­ti­cal uses for tele­por­ta­tion.

The Chi­nese sci­en­tists not only set a dis­tance record for tele­por­ta­tion, they also proved that it is pos­si­ble to build a work­able sys­tem for long-dis­tance quan­tum com­mu­ni­ca­tions. That could rev­o­lu­tion­ize elec­tronic com­mu­ni­ca­tions by mak­ing it im­pos­si­ble for out­siders to lis­ten in with­out alert­ing the user, a ma­jor ad­vance in the se­cu­rity of on­line traf­fic.

In these times, one may have to take such news with a pinch of salt. How­ever, Ox­ford Univer­sity physi­cist Ian Walm­s­ley ex­plained to the BBC that the tech­nol­ogy could even­tu­ally pro­vide the ba­sis for a cloud-based com­put­ing net­work that al­lows in­for­ma­tion to be sent se­curely. “It’s cer­tainly a sci­en­tific break­through,” he said of the Chi­nese achieve­ment.

China al­ready held the tele­por­ta­tion record, with a 2012 ex­per­i­ment that tele­ported in­for­ma­tion across 97 km. Up un­til now it had been im­pos­si­ble to cre­ate a longer-dis­tance quan­tum link be­cause an en­tan­gled pho­ton can only travel about 160 km along a fiber-op­tic ca­ble be­fore be­ing ab­sorbed.

By us­ing a satel­lite link, the Chi­nese team took ad­van­tage of the fact that pho­tons travel more eas­ily through space. The chal­lenge to over­come was that it had pre­vi­ously proved dif­fi­cult to trans­mit the par­ti­cles through the Earth’s at­mos­phere.

It is early days, but sci­en­tists in Ji­nan, Shan­dong prov­ince, have started tri­als on a se­cure net­work based on quan­tum tech­nol­ogy. And sci­en­tists in Bei­jing and Shang­hai are de­vel­op­ing a sys­tem that uses quan­tum nodes sit­u­ated about 96 km apart to mea­sure quan­tum sig­nals and send them on.

Brian Greene, a physics pro­fes­sor at New York’s Columbia Univer­sity, said the Chi­nese break­through evoked im­ages of Star Wars and Harry Pot­ter, in which wiz­ards dis­ap­pear from one lo­ca­tion only to re-emerge at an­other.

“It’s some­where in be­tween,” he told the US’ NPR net­work. “But hon­estly, you should be su­per ex­cited about that. It’s a crazy, won­der­ful thing that we can do this.”

The au­thor is a se­nior edi­to­rial con­sul­tant for China Daily. har­vey­mor­ris@gmail.com

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