Microwave antenna and quantum computing system

Abstract

A microwave antenna (1) is specified for emitting electromagnetic radiation provided to at least one ion (3) for quantum computation, comprising - a plurality of antenna elements (2) arranged spaced apart from one another, wherein - at least some of the antenna elements (2) are configured to emit electromagnetic radiation with a different phase from one another. Further, a quantum computing system (10) is specified.

Description

[0001]P2024,0040 WO N / IDF-HW-61 April17,2025 -1 - Description MICROWAVE ANTENNA AND QUANTUM COMPUTING SYSTEMThe present disclosure relates to a microwave anten na foremitting electromagnetic radiation provided to at l east oneion for quantum computation and a quantum computing system.Typically, for microwave-controlled trapped ion qub its, amicrowave intensity at a location of the trapped io n definesthe speed with which a qubit-state can change. Exem plarily, aratio of achievable microwave field strength to irr adiatedpower limits a gate speed or qubit number due to th edissipative heating of the ion trap, which is in pa rticularcriticalforoperating the ion trap in a cryogenic environment.An object to be solved is to provide a microwave an tennawhich hasan improved magneticfield distribution.Furthermore, a quantum computing system is to be pr ovided.The object is solved by the subject matter of the i ndependentclaims. Advantageous embodiments, implementations a nd furtherdevelopments are the subject matter of the respecti vedependentclaims.According to at least one embodiment, the microwave antennais configured to emit electromagnetic radiation pro vided toat least one ion for quantum computation. Exemplari ly, themicrowave antenna is configured to provide electrom agneticradiation to an ion trap with a processing region. Theprocessing region is in particular configured to ho st atleast one ion, exemplarily a plurality of ions. Exe mplarily, P2024,0040 WO N / IDF-HW-61 April17,2025 -2 -at most 100 ions or at most 60 ions are provided in theprocessing region. Exemplarily, the microwave anten na isconfigured to provide the electromagnetic radiation to theionsin the processing region.The ion trap can be a Paul trap, a linear ion trap, a surfaceion trap or a multi-layer ion trap. The ion trap co mprises,for example, a set of electrodes configured to conf ine and / ormanipulate at least one ion at a processing region. Forexample,a radio frequency,RF,voltage isapplied to atleast some electrodes of the set of electrodes such that atime-varying electric field is provided in the proc essingregion configured to confine and / or to manipulate t he ion.For example, the ion intersects with a trapping axi s and / oroscillates around a trapping axis within the proces singregion.Exemplarily, the electromagnetic radiation, in part icular amicrowave radiation, is applied to at least some tr appedions,in particular,bythe microwave antenna.Theelectromagnetic radiation is, for example, configur ed toinduce a transition between the energy levels of at leastsome ofthe trapped ions.Exemplarily,byapplying theelectromagnetic radiation, an operation on the quan tum statesof the trapped ions, such as qubit rotations or sta tepreparations,isperformed.Microwave radiation is in particular characteristic forelectromagnetic radiation with a frequency of at le ast 0.1GHz and at most 500 GHz, in particular at least 0.3 GHz andatmost300 GHz. P2024,0040 WO N / IDF-HW-61 April17,2025 -3 -The ion trap comprises, for example, at least one m agnetarrangement configured to establish a magnetic fiel d in theprocessing region. The at least one magnet arrangem ent cancomprise atleastone permanentmagnetarrangement and / oratleast one coil. The at least one magnet arrangement is, forexample, spaced apart from the processing region in lateraldirections and / or in vertical direction. In particu lar, theat least one magnet arrangement is configured to es tablish agradient of magnitudes of the magnetic field in theprocessing region, e.g. along the trapping axis. Th is isbecause the magnetic field of the magnet arrangemen t hasdifferent magnitudes for different positions in theprocessing region and in particular for different p ositionson the trapping axis. Advantageously,ifthere isa pluralityofionsin the processing region,the resonance frequencyofeach oftheions on which the gradient of magnitudes of the mag neticfield of the magnet arrangement acts, is unique for each ionin the processing region.According to at least one embodiment, the microwave antennacomprises a plurality of antenna elements which are arrangedspaced apart from one another. Exemplarily, the ant ennaelements comprise a top surface and a bottom surfac e oppositethe top surface, wherein the top surface and the bo ttomsurface are connected by at least one side surface. Forexample, side surfaces of directly neighboring ante nnaelementsface one another.In particular,the side surfacesof directly neighboring antenna elements are not in directand immediate contact with one another. For example , aminimal distance of the side surfaces of directly n eighboringantenna elements is at most 5 mm, at most 3 mm or a t most 2 P2024,0040 WO N / IDF-HW-61 April17,2025 -4 -mm, approximately 1 mm. Exemplarily, the minimal di stance ofthe side surfaces of directly neighboring antenna e lements isatleast0.1 mm oratleast0.5 mm.Exemplarily, the antenna elements comprise an elect ricallyconductive material. In particular, the antenna ele mentscomprise orconsistofa metal.Exemplarily, the minimal distance is characteristic for anangular resolution of the microwave antenna. The an gularresolution is, in particular, characteristic of the width ofthe main lobe of the emitted electromagnetic radiat ion of themicrowave antenna.According to at least one embodiment of the microwa veantenna,atleastsome ofthe antenna elementsare configured to emitelectromagneticradiation with a different phase fromone another. In particular, each of the antenna ele ments isconfigured to emita beam,in particularmicrowave radiation,wherein each beam is characteristic for electromagn eticradiation with a phase. At least some or all phases are inparticular different from one another. Particularly , at leastsome orallbeamsare configured to be provided to the ion as the emitted electromagneticradiation.Exemplarily, a predetermined phase and / or a predete rminedamplitude ofthe emitted electromagneticradiation atthelocation of the ion is predetermined dependent on t he phasesand in particular the amplitudes of the electromagn eticradiation of the beams. Advantageously, beam steeri ng and / orphase alignment can be advantageously realized at t helocation ofthe ion. P2024,0040 WO N / IDF-HW-61 April17,2025 -5 -In particular, the phases of individual beams are d eterminedsuch that individual beams create a converging wave frontcharacteristic for a predetermined maximum intensit y of theemitted electromagnetic radiation at the location o f the ion.Exemplarily, each of the antenna elements is connec ted to asignal line. All signal lines are, for example, com prised bya feeding network configured to distribute electric al signalsto the individual antenna elements via the signal l ines. Theelectrical signals are, for example, characteristic ofmicrowave frequency signals. In particular, each el ectricalsignal is characteristic for a phase of the respect ive beamto be emitted. Each phase is adjustable independent ly fromone another, exemplarily via the electrical signals .Exemplarily, the signal lines do not leverage any o pticalwaveguides and / or any photonics for signal transmis sion,modulation, and processing. For example, the signal linesconnected to the individual antenna elements compri ses,particularly exclusively, electrical conductors and / ordielectricmaterials.It is an idea, inter alia, to use a microwave anten na with aplurality of individual adjustable and / or controlla bleantenna elements to provide electromagnetic radiati on to thetrapped ion to perform quantum computational proces ses. Withsuch a microwave antenna,dissipative heating isadvantageously reduced in comparison to typical mic rowaveantennasforion traps,while the intensityoftheelectromagnetic radiation at the trapped ions' posi tion ismaintained orimproved. P2024,0040 WO N / IDF-HW-61 April17,2025 -6 -According to at least one embodiment of the microwa veantenna,the antenna elementsare arranged atgrid pointsofa grid. The grid points are characteristic of a cen ter ofeach of the antenna elements, in particular a cente r of mass.The grid is, for example, a circular grid, a linear grid or apolygonal grid, such as a triangular grid or a quad rangulargrid. Exemplarily, the antenna elements are arrange d at atleastsome ofthe grid points. Forexample,the grid pointsare spaced apartfrom oneanother by at least 5 mm and / or at most 2 cm, exemp larily 1cm.According to at least one embodiment of the microwa veantenna, the antenna elements are arranged in a n × marrangement, where n and m are each a natural numbe r largerthan two. Exemplarily, n and m are different to one anotherorn and m are equal.Preferably,n and m are each atleast3 oratleast6.According to at least one embodiment of the microwa veantenna, each of the antenna elements has a main ex tensionplane. For example, the main extension plane of eac h of theantenna elementsisparallelto the respective top surfaceand / or the respective bottom surface of the respect iveantenna element.According to at least one embodiment of the microwa veantenna,the main extension planesare in a common plane.Inparticular, lateral directions are oriented paralle l to thecommon plane and a verticaldirection isorientedperpendicular to the common plane. In particular, t he topsurfaces of each microwave antenna and / or the botto m surface P2024,0040 WO N / IDF-HW-61 April17,2025 -7 -of each microwave antenna are parallel to the commo n plane.Exemplarily, the top surfaces do not protrude beyon d oneanotherin verticaldirection facing the ion trap.According to at least one embodiment of the microwa veantenna, the antenna elements are arranged on a mou nt. Forexample, the antenna elements are arranged directly on themount. The mount comprises a substrate and / or a car rier.Forexample,atleastsome ofthe signallinesare atleastpartly arranged on and / or within the mount. In part icular, atleast some of the signal lines are arranged on and / or withinthe substrate. The mountcomprises,forexample,a top elementon which the antenna elementsare arranged.The top elementcan comprise orconsistofa dielectricsubstrate.Exemplarily, the mount comprises a back element fac ing awayfrom the antenna elements. The back element can com prise orconsist of a carrier particularly comprising alumin ium, steelorcomposite materials,particularlyforproviding mechanical stability.The backelementcan comprise a coating such as copper,gold orsilver,particularlyforenhancing electrical performance.For example, the mount can comprise a flexible subs trate,such asa polymercomposite ora metalalloy.Exemplarily, the signal lines can be partially embe dded inthe mount. P2024,0040 WO N / IDF-HW-61 April17,2025 -8 -According to at least one embodiment of the microwa veantenna, the emitted electromagnetic radiation comp rises anear field region, where the ion is configured to b e located.The beams emitted from neighboring antenna elements interactwith one another, forming the emitted electromagnet icradiation having a near field region and a far fiel d region.Exemplarily, the near field region is within a dist ance ofapproximately one wavelength from the microwave ant enna,wherein the far field region extends at distances s everaltimes larger than a wavelength of the emitted elect romagneticradiation.The near field region is, for example, characterist ic of adistance of at most 1.5 times or at most 1 times of awavelength of the emitted electromagnetic radiation . Thismeans that a distance between the antenna element a nd the ionis, for example, at most 1.5 times or at most 1 tim es of awavelength of the emitted electromagnetic radiation .Advantageously, the emitted electromagnetic radiati on in thenear field region can transfer power with comparati velyhighly efficiency in contrast to the far field regi on. Inparticular,in the nearfield region,the emittedelectromagnetic radiation, i.e. the beams, are morelocalized,allowing fora focused energytransfer. Further,such a microwave antenna is advantageously particul arlycompact in size such that it can be combined with a n ion trapwithout dramatically increasing the size of the sys tem.Exemplarily, the phases of the emitted electromagne ticradiation of different antenna elements are predete rminedsuch that an intensity of the emitted electromagnet ic P2024,0040 WO N / IDF-HW-61 April17,2025 -9 -radiation is maximized in the near field region, wh ere theion isconfigured to be located.According to at least one embodiment of the microwa veantenna,the phasesofthe emitted electromagnetic radiationof different antenna elements are predetermined suc h that theintensityofthe emitted electromagneticradiation isminimized in a predetermined region, different to t heprocessing region. Exemplarily, the phases of the e mittedelectromagnetic radiation of different antenna elem ents arepredetermined such that an intensity of the emittedelectromagnetic radiation is minimized at the prede terminedregion in the farfield region.Advantageously, such a microwave antenna can also b e appliedto a surface ion trap,e.g.a chip ion trap.According to at least one embodiment of the microwa veantenna,atleastsome ofthe antenna elementsare connected to an active phase shifter. Exemplarily,the active phase shiftercomprisesat leastoneelectronic component. The electric component compri ses, forexample, a transistor, e.g., a field-effect transis tor and / ora bipolar junction transistor, diodes, and / or integ ratedcircuits. The active phase shifter is configured todynamically control the phase of at least some or a ll of theantenna elements. The active phase shifter is in pa rticularconnected to at least some or all of the signal lin es.The active phase shifteris,forexample,arranged on themount or on an external control device. Exemplarily , theexternal control device is arranged spaced apart fr om the P2024,0040 WO N / IDF-HW-61 April17,2025 -10 -microwave antenna. The external control device is i nparticular connected to the microwave antenna by th e signallines.Advantageously, the phases can be continuously cont rolled byusing the active phase shifter, wherein a precise a djustmentof the phase angles is achieved for the different b eams.Thus,beam steering and / orphase alignmentcan be advantageouslyrealized.Furthermore, using an active phase shifter advantag eouslyleadsto a minimization ofinsertion losses.According to at least one embodiment of the microwa veantenna,atleastsome ofthe antenna elementsare connected to a passive phase delaying feed line.The passive phasedelaying feed line comprises, for example, a coaxia l cable,and / or a microstrip line. Exemplarily, a phase of t he beamsis dependent on a length of the passive phase delay ing feedline. The phases can be predetermined by predetermi ning thelengthsofthe passive phase delaying feed line.Exemplarily, at least some of the signal lines comp rises theat least some passive phase delaying feed lines. Inparticular, each signal line connected to an antenn a elementbeing connected to a passive phase delaying feed li ne,comprises the respective passive phase delaying fee d line.Exemplarily, the passive phase delaying feed line i s formedby increasing a length of the respective signal lin e.Forexample,the antenna elementsare connected to the signallines, which exclusively comprise the passive phase delayingfeed lines. This is in particular different from an active P2024,0040 WO N / IDF-HW-61 April17,2025 -11 -beam steering, e.g. a beam shaping by the active ph aseshifters.Forexample,the phasesofthe emittedelectromagnetic radiation of different antenna elem ents arepredetermined dependent on a geometry of the ion tr ap, andthe passive phase delaying feed linesare used for providingthe predetermined phases. In this case, the predete rminedphases do not change, as the focus of the electroma gneticradiation isfixed to the location ofthe ion.Advantageously, a simple, reliable, and cost-effect ive phasedifference ofthe antenna elementscan be achieved byusing the passive phase delaying feed line.By using the passive phase delaying feed lines, thi sadvantageously does not introduce extra noise in th e system.Therefore, the microwave antenna with the signal li nesexclusively comprising the passive phase delaying f eed linescan be advantageously used for qubit control, as no isedirectlyimpactsqubitfidelities.Exemplarily, the antenna elements are configured to beconnected to the active phase shifter and / or passiv e phasedelaying feed line.Furthermore, a quantum computing system is specifie d, whereinthe quantum computing system comprises the microwav e antennadescribed herein above. This is to say that the fea turesconcerning the microwave antenna are also applicabl e for thequantum computing system and vice versa.According to at least one embodiment, the quantum c omputingsystem comprisesan ion trap configured to provide the at P2024,0040 WO N / IDF-HW-61 April17,2025 -12 - leastone ion,asdescribed in connection with the microwave antenna.The ion trap with the microwave antenna can be oper ated atroom temperature and / or operated at a cryogenic tem perature.According to at least one embodiment, the quantum c omputingsystem comprises a cryostat configured to provide a cryogenicenvironment.The cryostatisconfigured to provide thecryogenic environment which has a temperature of at most 50 Koratmost20 K and / oratleast0.1 mK oratleast 0.3 mK.According to at least one embodiment of the quantum computingsystem,the microwave antenna and the ion trap are arranged within the cryogenicenvironment.The cryostat,in particularthe cryogenic environment, is configured to cool th emicrowave antenna and the ion trap. Exemplarily, at least oneof the microwave antenna and the ion trap are confi gured tobe thermally conductively connected to a cooling st age of thecryostat.In the following, the microwave antenna and the qua ntumcomputing are explained in more detail with referen ce toexemplaryembodimentsand the associated figures.Figure 1 shows a schematic view of the microwave an tennaaccording to an exemplaryembodiment.Figure 2 shows a schematic view of the quantum comp utingsystem according to an exemplaryembodiment.Elements that are identical, similar or have the sa me effectare given the same reference signsin the figures. The P2024,0040 WO N / IDF-HW-61 April17,2025 -13 -figures and the proportions of the elements shown i n thefigures are not to be regarded as true to scale. Ra ther,individual elements may be shown exaggeratedly larg e forbetter representability and / or for better comprehen sibility.The microwave antenna 1 according to the exemplary embodimentof Figure 1 comprises a plurality of antenna elemen ts 2arranged spaced apart from one another. The antenna elements2 are arranged at grid points of a grid, in particu lar aregular grid. The antenna elements 2 according to t hisembodiment are arranged along a linear grid, partic ularly anarray. Preferably, the antenna elements 2 are arran ged atgrid pointsofa quadrangulargrid.Each of the antenna elements 2 are connected to a r espectivesignal line 14. The signal lines 14 are connected t o anexternal control device. The external control devic e isconfigured to provide an electricalsignalto each oftheantenna elements 2. Further, the external control d evice isin particulara generator8 configured to generate anelectrical signal with a microwave frequency. Exemp larily,the generated electricalsignalisprovided to all antenna elements2.Each of the antenna elements 2 is configured to emi t a beamof electromagnetic radiation dependent on the elect ricalsignal.In particular,each beam ischaracteristic ofmicrowave radiation with a phase. Further, each be am isparticularlycharacteristicofmicrowave radiation with an amplitude.Each phase and / oreach amplitude can bepredetermined. Each phase corresponding to a respec tive beamis predetermined and adjusted in such a way that co nstructiveinterference iscreated in a desired direction,in particular P2024,0040 WO N / IDF-HW-61 April17,2025 -14 -at the trapped ions' position. Additionally, each a mplituderespective beam is predetermined and adjusted in su ch a waythat a predetermined signal strength and predetermi nedqualityiscreated. Each ofthe antenna elements2 are connected to an active phase shifter6,in particularbya furthersignal line 16different from the signal line 14. The active phase shifter 6is configured to provide a further electrical signa l to eachof the antenna elements 2 for changing the phase. I nparticular, the phase of a respective beam is depen dent onthe further electrical signal. Alternatively or add itionally,a passive phase delaying feed line 7 is comprised b y at leastone ofthe signallines14 forchanging the phase.At least some of the antenna elements 2 are configu red toemit electromagnetic radiation with a different pha se fromone another. In particular, at least some of the be amsemitted from the at least some of the antenna eleme nts 2 havephasesdifferentfrom one another.All of the beams interact with one another and form theelectromagneticradiation emitted bythe microwave antenna 1. In particular,the electromagneticradiation hasa convergingwave front formed by the beams. The emitted electro magneticradiation, i.e. the wave front, is illustrated by t he dashedlines facing the ion trap 4 with the ion 3. Advanta geously,the phasesofindividualbeamsare determined such that individualbeamscreate the converging wave frontcharacteristic for a predetermined maximum intensit y of theelectromagnetic radiation at the location of the io n 3. P2024,0040 WO N / IDF-HW-61 April17,2025 -15 -The emitted electromagnetic radiation is provided t o an ion 3trapped in an ion trap 4. The microwave antenna 1 a nd the ion3 are spaced apartfrom one anotherbya distance, whereinthe distance is characteristic for a near field reg ion 5 ofthe emitted electromagnetic radiation. This means t hat thedistance between the microwave antenna 1 and the io n 3 is atmost 1.5 times or at most 1 times of a wavelength o f theemitted electromagneticradiation.The ion trap 4 comprises in particular a set of ele ctrodes15, wherein a radio frequency, RF, voltage can be a pplied toat least some electrodes 15 such that a time-varyin g electricfield is provided in a processing region configured to trapthe ion 3.The quantum computing system 1 according to the exe mplaryembodiment of Figure 2 comprises a quantum processo rcomprising the ion trap 4 and the microwave antenna 1 whichare arranged in a chamber 9, providing a vacuum env ironmentand / or a cryogenic environment. The quantum process or and apossible laser system are connected by means of con nections11 to a control electronics system 12, which is con nected toa device 13 being a classicalcomputerdevice.The invention is not limited to the exemplary embod iments bytheir description. Rather, the invention encompasse s any newfeature as well as any combination of features, whi ch inparticularincludesanycombination offeaturesin the claims,even ifthisfeature orcombination itself isnotexplicitly indicated in the claims or exemplary emb odiments. P2024,0040 WO N / IDF-HW-61 April17,2025 -16 - Reference signslist 1 microwave antenna 2 antenna elements 3 ion 4 ion trap 5 nearfield region 6 active phase shifter 7 passive phase delaying feed line 8 generator 9 chamber 10 quantum computing system 11 connections 12 controlelectronicssystem 13 device 14 signallines 15 electrodes 16 furthersignalline

Claims

P2024,0040 WO N / IDF-HW-61 April17,2025 -17 - Claims1. Microwave antenna (1) for emitting electromagnet icradiation provided to at least one ion (3) for quan tumcomputation,comprising- a plurality of antenna elements (2) arranged spac ed apartfrom one another,wherein- at least some of the antenna elements (2) are con figured toemit electromagnetic radiation with a different pha se fromone another.

2. Microwave antenna (1) according to claim 1, wher ein- the antenna elements (2) are arranged at grid poi nts of agrid.

3. Microwave antenna (1) according to any one of cl aims 1 or2,wherein -the antenna elements(2)are arranged in a n × marrangement, where n and m are each a natural numbe r largerthan two.

4. Microwave antenna (1) according to any one of cl aims 1 to3,wherein- each of the antenna elements (2) has a main exten sionplane,and -the main extension planesare in a common plane.

5. Microwave antenna (1) according to any one of cl aims 1 to4,wherein- the antenna elements (2) are arranged on a mount.

6. Microwave antenna (1) according to any one of cl aims 1 to5,whereinP2024,0040 WO N / IDF-HW-61 April17,2025 -18 -- the emitted electromagnetic radiation comprises a nearfield region (5), where the ion (3) is configured t o belocated.

7. Microwave antenna (1) according to any one of cl aims 1 to6,wherein- at least some of the antenna elements (2) are con nected toan active phase shifter(6).

8. Microwave antenna (1) according to any one of cl aims 1 to7,wherein- at least some of the antenna elements (2) are con nected toa passive phase delaying feed line (7). 9.Quantum computing system (10),comprising- the microwave antenna (1) according to any one of claims 1to 8,and- an ion trap (4) configured to provide the at leas t one ion(3).

10. Quantum computing system (10) according to clai m 9,furthercomprising- a cryostat configured to provide a cryogenic envi ronment,wherein- the microwave antenna (1) and the ion trap (4) ar e arrangedwithin the cryogenicenvironment.

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