PC Pro - UK 2021-12)

ofthosephysicalobjectstocalculate

andsimulatetheirrelationships.

Moreprecisely,bitslivebetweenthe

physicalandyetanotherworld,the

quantumworld,whichfollows

different,weirder,rulesthatallow

“entanglement”toeradicatedistance

andseparation.Bitsareelectrical

chargesstoredinsiliconcapacitorsor

similar, andattoday’stinyfeature

sizestheyfeel thatweirdness.My

scepticism towardthecurrenthype

overquantumcomputersgrowsfrom

a suspicionthatmanyquantum

enthusiaststhink“quantum”isgoing

tofree us fromthe confinesofboring

oldphysicality,whichitisn’t.

T

hephysicalworldisruledby

thelawsofthermodynamics.

Themostreadable accountof

thoselawsisPeterAtkins’ 1984 book

TheSecondLaw, in whichhe

explainsthatmanythingsinthe

worldareengines thattakein energy,

turnsomeofitintowork, andexpel

the“waste”asheat. Forexample,we

takeinglucose andrunaround

thinking,while chipssteerelectrons

toperformBooleanoperations.

I wasintroducedtoAtkins’book

bymybrother-in-lawPipHills,who

likemewasfascinatedbymotorsand

machines– we oncedrovetoPrague

togetherinhis 1937 Lagonda,fitted

witha largeGardnerdiesel engine

(pcpro.link/ 326 lagonda).Pipstudied

philosophy,butwesharethatfaithin

thermodynamicsasa wayto

understandthelimitsofthephysical

world.A fewyearsago,he bought a

ratherfineoldworkingmodelofan

odd-looking engine in Portobello

Road:wetookit

home,plonkedit

ona gasringandit

startedrunning.

Onceback

homein Scotland,

Pipbegantostudy

thehistoryofthis

I

f there’san underlyingtheme to

thiscolumn,whichmaybe

doubted,thenit’sthedifference

betweenthephysicalandthedigital

worlds.I cansumitupinanaphorism

I’veemployedfartoomanytimes:

“Youcanordera pizza online,butyou

can’teatitonline”.I’vebeenlivingin

thisgapbetweenworldsfor 40 years

now:my firsttoeinthedigitalwater

wasviaa CommodorePETin 1 981 at

thestartofthe personalcomputer

revolution,though it wasn’tuntilthe

comingofWWW that we allgot

properlyconnectedtogether.

Ofcourse,I wasbornintothe

physicalworld,andinhabiteditwith

increasingcuriosity throughouta

childhoodfilledwithMeccano(Ibuilt

thetravellinggantry!) andmodel

aeroplaneswith glow-plugengines(I

wasina control-linecombatteam).

AtschoolI immersed myselfin

science andmycollegelabdayswere

prettyphysical: hot,smellyandtoxic

inchemistry;warm,wet,saltyand

mildlyradioactiveinbiochemistry.I

droppedoutandstumbledintothe

digitalworldwhenDennisPublishing

acquiredPersonalComputerWorld

magazineinthelate 1970 s,merely

becauseI wasthemostnumerate

personpresent, thoughmyprevious

experience hadbeenhandinga

printouttoa manina labcoatand

gettingtheresultsbackonTuesday.

Thephysicalworldisfilledwith

palpable, even edible,objectsmadeof

atomsandmoleculesthatwhizz

roundsubjecttorulesweweretaught

inphysicsand chemistry,whilethe

digitalworldconsistsofbitswith

whichweconstructrepresentations

unusualheatengine,becomingso

intrigued thathe’swrittena book

aboutitcalledTheStarDrive(Birlinn,

2021).Heexplainshowtheengine

wasinventedbyScottishparson

RobertStirlingin1816,anditrunsby

expanding hotairratherthansteam.

Itdiffersfrominternalcombustion,

petrolordieselenginesbyusingan

externalheatsource.

Simplerandwith fewermoving

partsthansteamengines,Stirling

enginesneverthelesslostoutasthe

hightemperaturestheyrequired

brokeavailablematerialssuchascast

ironandleather,andalsobecause

theirspeedisn’teasyto control.

But,morerecently,theirability to

operatecompletelysealed fromthe

outsideworldexcept fora heatsource

hasopened up several interesting

nicheapplications.

TheSwedishnavy operatessmall

non-nuclearsubmarinespoweredby

Stirlingenginesburningliquid

oxygenanddieselfuelcatalyticallyto

chargebatteries. Oneofthese

humiliatedtheUSS RonaldReagan

during 2005 wargames by

penetratingitsdefencesto“paintball”

it.NASAusesclosed-cycleStirling

enginesheatedbynuclearreactorsto

generateelectricityinspacecraft

travellingtotheoutersolarsystem,

wheretheyoperateforyearswithout

sunlight, lubricationor maintenance.

AndminiatureStirlingenginesdriven

backwardbyexternalelectromagnets

makehighlyefficientheat pumpsfor

cryogenic cooling– perhapstokeep

somefuture quantumcomputer

withinitsownchillyworld.

[email protected]

Manyquantumenthusiasts

think“quantum”isgoingtofree

usfromtheconfinesofboringold

physicality,whichitisn’t

Bitslivebetweenthephysical

andyetanotherworld,the

quantumworld,whichfollows

different,weirder,rules

Sterlingservice

fromStirling

engines

DickPountain

nowadaysexpels

mostwasteheat

viathetopofhis

head.Whennot

beingasourceof

heat,he’seditorial

fellowofPCPro.

Thehypeaboutquantumcomputingcontinuestogrow,butthelawsof

thermodynamicswillcontinuetokeepusgrounded