Method and apparatus for addressing qubits and method for manufacturing the apparatus

Abstract

The present invention relates to a method for addressing qubits (14, 16), a device (10) for addressing qubits (14, 16), and a method for manufacturing the device (10). Thus, qubits (14, 16) can be addressed in a simple manner without the risk of crosstalk between different qubits (14, 16). Here, different qubits (14, 16) can be addressed individually and jointly. In addition, it is also possible to easily read out the qubits (14, 16).

Description

Technical Field

[0001] The present invention relates to a method for addressing qubits, an apparatus for addressing qubits, and a method for manufacturing the apparatus. Background Art

[0002] Quantum computers offer the possibility of solving special problems by means of quantum mechanical effects.

[0003] Different from commercially available computers, qubits are used herein, which are equivalent to bits in classical computers.

[0004] Consideration of bits shows that they can only have two states. These two states are 0 and 1. In contrast, a qubit can not only assume the states 0 and 1, but can also assume intermediate states between 0 and 1 for a certain period of time (coherence time). This state is called superposition.

[0005] Therefore, compared with classical bits of current computers, qubits can process more information, thus providing the potential for a computer with unprecedented computing power. In particular, the production of such qubits is currently a subject of intensive research in the scientific community. Scientists are looking for the best methods to generate qubits and connect them to each other into computing units according to the laws of quantum mechanics.

[0006] Qubits can currently be implemented by different methods.

[0007] It is well known that superconducting qubits are easy to construct and expand. Up to 20 qubits have been entangled in this way. However, there is only a very short T2 time (transverse relaxation time - spin - spin relaxation), and cooling to 4°K (-273°C) must be ensured. Therefore, the computer must be installed in a specially provided room to ensure cooling and prevent vibrations, stray electric fields, and waste heat as much as possible.

[0008] Qubits by ion traps are easy to control and have a very long T2 time. 10 to 20 qubits have been entangled in this way. But they are not scalable and are very complex technically.

[0009] NMR quantum computers have also been studied, in which 5 qubits have been entangled. They are characterized by very simple programming, but they are not scalable and the technology behind them is very complex.

[0010] So far, solid - state - based qubits are the only way to circumvent the above - mentioned disadvantages, because a quantum computer operating with solid - state - based qubits can operate at room temperature. In addition, it is scalable and CMOS - compatible, so it can be well connected to the semiconductor technology used so far.

[0011] The present invention is based on such solid-state qubits. The currently most promising variant of solid-state qubits is the use of nitrogen-vacancy centers (NV centers) in diamond.

[0012] Diamond has various mechanical properties, such as extremely high hardness, thermal conductivity, and chemical inertness. In recent years, it has been possible to successfully produce diamond by chemical vapor deposition (CVD). The advantage of synthetic production is that diamond can be fabricated with high isotopic purity and specific crystal defects. Therefore, diamond can be equipped with application-specific optical and electronic properties. These properties of diamond that can now be determined are very important for quantum mechanics and there are large application areas here.

[0013] A two-dimensional lattice of NV centers can be created in synthetic diamond. Here, the nuclear spin of the nitrogen atom serves as a qubit; readout and coupling are performed through the electron spin of the NV center, where the coupling is achieved through magnetic dipole interaction; a non-uniform magnetic field enables individual quantum gates and parallel gate operations on many qubits. However, addressing individual gate operations and reading out individual qubits is a particular problem.

[0014] Local addressing (shifting the resonance frequency by at least one linewidth) can generally be achieved by using a magnetic field or qubits in different directions. The necessary shift depends on the T2 time. The problem here is that when applying the resonance shift, the influence of adjacent qubits (so-called cross talk or crosstalk) cannot be completely avoided.

[0015] An alternative method is optical addressing, as described in US 9,317,473 B2. Here, the addressing is done optically. To avoid crosstalk between different qubits (registers), they must be arranged far enough apart (400 nm to 500 nm). However, for these distances, direct entanglement of the qubits does not occur, so entanglement must be mediated through the so-called dark spin chain of optically non-addressable spins. Conversely, if the distance is small enough for direct entanglement, the addressing is performed through a near-field microscope (Spin-Resolft). However, indirect entanglement involves functional risks and using a near-field microscope for each individual register is very complex. In addition, crosstalk cannot be excluded in either case. Summary of the Invention

[0016] Therefore, the object of the present invention is to be able to address qubits in a simple manner without the risk of crosstalk. In particular, it should also be possible to easily read out the qubits.

[0017] The present inventor has recognized that this object can be achieved in a surprising manner and method, namely, by means of an electromagnetic field for addressing qubits, without the addressed qubits being shielded by an appropriate reverse electromagnetic field. Thus, each individual qubit in a set of more than two qubits can be addressed very precisely and at the same time easily, even if they are arranged relatively close to each other for the purpose of direct entanglement.

[0018] The method according to the invention for addressing at least one qubit in a set of more than two qubits is characterized in that the qubit to be addressed is exposed to an electromagnetic field, while at least one other qubit in the set of qubits is exposed to a reverse electromagnetic field, such that the electromagnetic field has no effect on the other qubits (for purely shielding the other qubits), or such that the effect of the electromagnetic field on the other qubits is different from the effect on the qubit to be addressed (for different addressing).

[0019] In the context of the present invention, "addressing" is not only understood as selecting a qubit to change its state, but also means the actual change of its state in the context of a quantum gate operation (also referred to as Quantum Gate Operationen). The gate operation can be a single-gate or two-gate or multi-gate operation; the latter usually depends on the state of the qubits (e.g., CNOT gate). Thus, the "method for addressing a qubit" according to the present invention is more precisely a "method for selecting a qubit and / or for changing the state of a qubit".

[0020] Thus, addressing is accomplished by selecting the desired qubits and performing quantum gate operations on these qubits. At the same time, other qubits are shielded or the reverse field is adjusted such that their own quantum gate operations are optimized.

[0021] The quantum gate operation is based on, for example, the change in the spin state of a qubit due to the influence of a time-varying magnetic field of a specific duration. Here, the pulse shape is set to achieve a well-defined state with a low error rate. In the case of entangled qubits, multiple qubits can be addressed simultaneously for control register and error correction. Generally, for an electron spin system, the pulse waveform uses a carrier frequency in the frequency range of 500 MHz to 50 GHz, and for a nuclear spin system, the pulse waveform uses a carrier frequency in the frequency range of 1 kHz - 100 MHz.

[0022] The exact process of quantum gate operation is not the subject of the present invention. It can be obtained, for example, from the article "Proteting a Diamond Quantum Memory by Charge State Control" by M. Pfender et al., Nano Lett. 2017, 17, 10, 5931-5937, the relevant content of which is hereby incorporated herein by reference in its entirety.

[0023] Here, the electromagnetic field and the reverse electromagnetic field are specifically coordinated according to the electromagnetic source and the position of the qubit relative to the source to respectively achieve the desired addressing or non-addressing of the qubit.

[0024] Due to the linearity of Maxwell's equations, each individual qubit can be separately addressed differently. Specifically, the following addressing types can be achieved:

[0025] - Each qubit can be separately addressed at a specific time point without addressing other qubits;

[0026] - Two or more qubits can be addressed identically at the same time without addressing other qubits;

[0027] - Two or more qubits can be addressed differently at the same time without addressing other qubits;

[0028] - Two or more qubits can be addressed identically at the same time while addressing at least one other qubit differently and not addressing the remaining qubits;

[0029] - Two or more qubits can be addressed identically at the same time while addressing the remaining qubits differently;

[0030] - All qubits can be addressed differently at the same time.

[0031] Here, since the reverse electromagnetic field is specifically adjusted for the addressing of each qubit relative to other qubits, there is no crosstalk between the addressings of the qubits.

[0032] Therefore, each qubit can be simultaneously exposed to the electromagnetic field and the reverse electromagnetic field, wherein the desired quantum gate operation and shielding are simultaneously achieved through the superposition of the electromagnetic field and the reverse electromagnetic field. Here, the electromagnetic field itself does not have to precisely serve the quantum gate operation of one qubit, and the reverse electromagnetic field does not have to precisely serve the shielding of another qubit, but a mixed form is possible. For example, the electromagnetic field of one qubit and the reverse electromagnetic field of another qubit can be used to achieve the quantum gate operation of another qubit.

[0033] In a favorable exemplary improvement, amplitude modulation is performed on the electromagnetic field and the reverse electromagnetic field, wherein there is a temporal variation between the modulation of the electromagnetic field and the modulation of the reverse electromagnetic field. Thus, the method can be implemented particularly easily and effectively.

[0034] In a favorable exemplary improvement, an electromagnetic near-field is used as the electromagnetic field and the reverse electromagnetic field, wherein preferably the electromagnetic near-field is a magnetic near-field particularly having frequencies in the microwave range and / or the kilohertz range. The electromagnetic near-field couples very well to adjacent qubits, wherein due to the Laplace equation, the largest field enhancement occurs near the source of the electromagnetic near-field. These near-fields are independent of the wavelength of the electromagnetic field or reverse electromagnetic field used and can be locally amplified or restricted by superposition. Fields in the kilohertz range (in the range of 0 kHz to 1 GHz) can be used to address nuclear spins, while fields in the microwave range (in the range of 0 GHz to 50 GHz, preferably in the range of 2.87 GHz) can be used to address electron spins.

[0035] In a favorable exemplary improvement, color centers (preferably, NV centers) in diamond are used as qubits. As shown in DE 102019 117 423.6, these color centers can be produced particularly easily and with a high conversion rate, the relevant content of which is hereby incorporated herein in its entirety.

[0036] In a favorable exemplary improvement, in order to provide the electromagnetic field and the reverse electromagnetic source, an electromagnetic source preferably in the form of a conductive structure assigned to each qubit is used. Thus, the electromagnetic field and the reverse electromagnetic field can be particularly easily locally assigned to each individual qubit.

[0037] In a favorable exemplary improvement, the conductive structure is provided as lines (Leitungen), metallization structures (Metallisierungen), wires for the electromagnetic field, preferably for the electromagnetic high-frequency field. Or the like. For this purpose, the conductive structure should in particular be able to transmit high frequencies. For this purpose, the conductive structure preferably has dimensions smaller than the distance between adjacent qubits (the diameter - the length may be larger). Thus, the method can be implemented particularly easily and effectively.

[0038] In a preferred embodiment, color centers are used as qubits, wherein the electromagnetic field and the reverse electromagnetic field are provided by a conductive structure having dimensions smaller than the distance between adjacent qubits. Thus, it is particularly easy to address the qubits.

[0039] In a favorable exemplary improvement, the number of conductive structures is the same as the number of qubits, so that addressing can be particularly easily performed.

[0040] However, the number of conductive structures does not have to be the same as the number of qubits, because the fields from different conductive structures can be superimposed and can also form a gradient field. To make the system underdetermined, an additional quasi-static electric field can be generated on the conductive structures and addressed, for example, by the Stark effect or the Zeeman effect. This results in a defined frequency shift and makes the other qubits effectively invisible to the electromagnetic field. In the simplest case, a defined bias voltage (e.g., 10 V) is applied to the lines, and the voltages only add up at the intersections (20 V) and result in the tuning frequency of the electromagnetic field. Thus, for example, quantum gate operations can also be performed simultaneously on two or three qubits. Then, the errors that occur due to the pulses associated with the bias voltage changes can be corrected by multiple pulse sequences separated in time.

[0041] Thus, a field consisting of, for example, 9 qubits can be addressed by 6 first conductive wires present in two layers, where these 9 qubits are arranged in an orthogonal 3×3 grid in the layers, with each layer having 3 first conductive wires arranged parallel to each other; the wires of one layer are orthogonal to the wires of the other layer, and the individual wires are arranged electrically insulated from each other.

[0042] Preferably, the wires extend respectively in a manner parallel to a row of qubits. Generally, a grid consisting of X*Y qubits can be addressed respectively by at least two layers with at least X wires or Y wires. Here, the grid and the wires do not necessarily have to be arranged orthogonally, they can also be arranged obliquely. In this case, the addressing is achieved, for example, by an electric field using the Stark effect or by a semi-static magnetic field using the Zeeman effect. In both cases, the resonance frequency of the qubits changes, which in turn leads to a selection effect.

[0043] On the other hand, in the case of three-dimensionally orthogonally or obliquely arranged qubits (X*Y*Z), the addressing can be carried out by at least three mutually orthogonal or oblique layers with at least X, Y, and Z wires. Here, the wires also preferably extend in a manner parallel to a row of qubits.

[0044] In principle, it is sufficient if there is a separate conductive structure (e.g., wire, line, or metallization structure) for each qubit. However, by arranging the qubits in a 2D or 3D grid, the number of required conductive structures can be reduced. Here, the individual conductive structures must in each case be arranged electrically insulated from each other, which can be achieved, for example, by an insulating material in the layer between the individual conductive structures and an insulating layer between different layers with conductive structures.

[0045] An electromagnetic source or a conductive structure can be used to read out qubits simultaneously. For this purpose, for example, photoelectrons are generated in the qubits to be read by a light pulse and detected by the electromagnetic source or the conductive structure. For this purpose, at least one additional grounding portion should be provided. Such a grounding portion can exist, for example, as a back contact of a thin layer, where the qubits are located in the thin layer, or there are one or more other conductive structures that are grounded.

[0046] The exact procedure for readout is not the subject of the present invention. It can be obtained, for example, in the article "Photoelectrical Imaging and Coherent spin-state readout of single nitrogen-vacancy centres in diamond" by P. Siyushev et al., Science, 363, 6428, 728 - 731, the relevant content of which is hereby incorporated herein by reference in its entirety.

[0047] In an advantageous exemplary improvement, the qubits are composed of a transparent material such that the qubits can be formatted by light radiation, preferably by laser radiation, preferably formatting multiple qubits simultaneously, in particular formatting all qubits simultaneously, as also described, for example, in the article "Photoelectrical Imaging and Coherent spin-state readout of single nitrogen-vacancy centres in diamond" by P. Siyushev et al., Science, 363, 6428, 728 - 731, the relevant content of which is hereby incorporated herein by reference in its entirety. If conductive structures are used as the electromagnetic source, these conductive structures should be formed as transparently as possible to avoid blocking the radiation. For example, it can be a line or wire made of a metal oxide such as ITO (indium tin oxide). In the case of an opaque conductive structure, the size of the conductive structure can be determined such that the radiation can reach the corresponding qubits by diffraction.

[0048] What is claimed to be independently protected is a device for addressing at least one qubit in a group of two or more qubits according to the present invention, characterized in that the device has a component for generating an electromagnetic field, which is designed such that the qubit to be addressed can be exposed to the electromagnetic field, and the device has a component for generating at least one reverse electromagnetic field, which is designed such that at least one other qubit in the group of qubits can be exposed to the reverse electromagnetic field, so that the electromagnetic field of the qubit to be addressed has no effect on the other qubits, or the effect of the electromagnetic field on the other qubits is different from the effect on the qubit to be addressed.

[0049] In an advantageous exemplary improvement, the device is suitable for performing the method according to the present invention.

[0050] In an advantageous exemplary improvement, the device has a first electromagnetic source, preferably a first conductive structure, in particular a line, wire, metallization structure and the like, for generating an electromagnetic field and a reverse electromagnetic field, wherein at least one electromagnetic source, preferably a first conductive structure, is assigned to each qubit. Thus, the electromagnetic field and the reverse electromagnetic field can be particularly easily assigned to the individual qubits.

[0051] In an advantageous exemplary improvement, a plurality of first electromagnetic sources, preferably in the form of wires and preferably first conductive structures, are arranged in a layer, wherein the distance of the qubits from their respective associated electromagnetic sources in a direction perpendicular to the layer is at most 30 nm, preferably at most 20 nm, in particular in the range from 0 nm to 10 nm. Thus, an electromagnetic near field can be particularly easily generated, which is very strongly coupled to adjacent qubits, wherein, due to the Laplace equation, there is a maximum field enhancement. These near fields are independent of the wavelength of the electromagnetic field or reverse electromagnetic field used and can be locally strengthened or restricted by superposition.

[0052] In an advantageous exemplary improvement, at least one first conductive structure can optionally be connected to an electromagnetic exciter or an optoelectronic detector. Thus, the conductive structure can be used both for addressing and for readout.

[0053] In an advantageous exemplary improvement, a plurality of first electromagnetic sources, preferably in the form of wires and preferably first conductive structures, are arranged in a layer, wherein the distance of the qubits projected onto the layer from their respective associated first electromagnetic sources is at most 20 nm, preferably at most 10 nm, in particular in the range from 0 nm to 5 nm. Thus, it is also possible to particularly easily generate an electromagnetic near field, which is very strongly coupled to adjacent qubits, wherein, due to the Laplace equation, there is a maximum field enhancement. These near fields are independent of the wavelength of the electromagnetic field or reverse electromagnetic field used and can be locally strengthened or restricted by superposition.

[0054] In a favorable exemplary improvement, the device has at least one second conductive structure, preferably a second conductive wire, line, metallization structure or electrode, which forms a ground portion for reading out the qubit, wherein the second conductive structure is preferably arranged adjacent to the first electromagnetic source, in particular at a distance of at most 40 nm, preferably at most 30 nm, especially in the range of 10 nm to 20 nm, in one layer.

[0055] In a favorable exemplary improvement, the device has at least one second conductive structure as a back contact of a relatively thin layer, wherein it is recommended that the layer thickness of the diamond is at most 100 nm, preferably at most 80 nm, especially at most 60 nm. Thus, reading can be carried out particularly effectively.

[0056] In a favorable exemplary improvement, i) the cross-section of the first conductive wire and / or the second conductive wire has a longitudinal dimension of less than 50 nm, preferably less than 20 nm, especially in the range of 1 nm to 10 nm, and / or ii) the length is less than 50 nm, preferably less than 30 nm, especially 5 nm to 20 nm. Thus, an electromagnetic near field can be generated particularly well.

[0057] In a favorable exemplary improvement, the qubits are arranged in a one-dimensional, two-dimensional or three-dimensional manner. Thus, a large number of qubits are particularly well interleaved with each other, and they can still be addressed independently of each other.

[0058] In a favorable exemplary improvement, the conductive structures are arranged in a one-dimensional, two-dimensional or three-dimensional manner, wherein preferably there are more than two layers, and the conductive wires are arranged parallel to each other in these layers, wherein the conductive structures of different layers are arranged differently, and an electrical insulator is preferably arranged between two layers. Thus, the qubits can be easily addressed and read out again. Preferably, the conductive structures of different layers are arranged obliquely to each other, preferably orthogonally to each other, because then an electromagnetic field with elliptical or circular polarization can be generated, thereby generating three-state particles (two-qubit transition, see the article "Room temperature entanglement between distant single spins in diamond" by F. Dolde et al., Nature Physics, 9, 139 - 143 (2013)).

[0059] In a preferred embodiment, the qubit is a color center, wherein the components for generating the electromagnetic field and the reverse electromagnetic field include a conductive structure having a size smaller than the distance between adjacent qubits. Thus, the qubits can be addressed particularly easily.

[0060] Furthermore, what is claimed to be independently protected is a method for manufacturing the device according to the present invention, characterized in that two or more qubits are generated in the surrounding material and a first conductive structure is arranged on the surrounding material.

[0061] In an advantageous improvement example, at least one of the following steps is also performed:

[0062] - Select a diamond layer (as a bulk material or as a layer on a substrate) as the surrounding material,

[0063] - Dope the surrounding material with a dopant (preferably sulfur, phosphorus, or oxygen),

[0064] - Perform a first tempering step after doping,

[0065] - Perform a second tempering step after generating the qubits,

[0066] - Lay a second conductive structure for reading out the qubits.

[0067] More detailed information about qubit generation can be obtained in DE 10 2019 117 423.6.

[0068] Conductive structures such as lines, wires, and metallization structures can be manufactured using various methods. On the one hand, printing can be carried out. Then coating can be done through a template. In addition, wires can also be directly written using, for example, an AFM probe, as described in the article "Atomic force microscope integrated with a scanning electron microscope for correlative nanofabrication and microscopy" by I.W. Rangelow et al., J. Vac. Sci. Technol. B 36(6), November / December 2018.

[0069] In a preferred embodiment, the generation of qubits can include the injection of foreign atoms, which corresponds to the method using an AFM probe described in the publication "Nanoscale Engineering and Optical Addressing of Single Spins in Diamond" by S. Pezzagna et al., Small 2010, 6, No. 19, 2117 - 2121, because the qubits can thus be very precisely positioned.

[0070] In a preferred embodiment, color centers are produced as qubits, and conductive structures are produced such that they have dimensions smaller than the distance between adjacent qubits. Thus, the qubits can be addressed more easily. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The features and other advantages of the present invention will become apparent from the following description of preferred exemplary embodiments in conjunction with the accompanying drawings. Here, the drawings schematically show the following:

[0072] Figure 1 A first preferred embodiment of the device according to the present invention is shown in a top view;

[0073] Figure 2 A side cross-sectional view shows the device according to Figure 1 the present invention;

[0074] Figure 3 A first preferred embodiment of the device according to the present invention is shown in a top view; and

[0075] Figure 4 A side cross-sectional view shows the device according to Figure 3 the present invention. DETAILED DESCRIPTION

[0076] In Figure 1 and Figure 2 a first preferred embodiment of the device 10 according to the present invention is shown in more detail.

[0077] It can be seen that the device 10 has a diamond bulk material 12, in which two qubits 14, 16 are arranged at a depth of about 10 nm below the surface 18 of the diamond material 12.

[0078] First conductive wires 20, 22 made of ITO (indium tin oxide) are arranged directly above the two qubits 14, 16. There is also a second conductive wire 24 formed of tungsten. For contact, these wires 20, 22, 24 each have a corresponding contact area 26 to which electrical connection terminals (not shown) can be connected respectively.

[0079] Two first wires 20, 22 for addressing and reading out the two qubits 14, 16 have a spacing of approximately 20 nm to 30 nm, which spacing thus also corresponds to the spacing between the two qubits 14, 16. Thus, these qubits 14, 16 can be easily entangled.

[0080] The second wire 24 forming the ground portion for reading out the qubits 14, 16 is arranged at the central position between the two first wires 20, 22, and thus has a spacing of 10 nm to 15 nm from these first wires 20, 22. All the wires 20, 22, 24 are arranged parallel to each other in a plane on the surface 18. They have a length of 5 nm to 30 nm, preferably 20 nm, in the straight region between the contact surfaces 26 (see Figure 2 ), and have a height and width of 1 nm to 10 nm, preferably 5 nm.

[0081] Now, the operating principle of the device 10 is to simultaneously format the qubits 14, 16 by a suitable laser pulse passing through the surface 18, and this laser pulse can easily reach the qubits 14, 16 through the transparent wires 20, 22 made of ITO. Here, due to the laser pulse, spin polarization occurs, and all the qubits 14, 16 enter the ground state. This provides a defined and known initial state (formatting).

[0082] Alternatively, the wires 20, 22 can also be formed of, for example, silver or gold. In this case, due to the very narrow size of the wires 20, 22, the laser pulse diffracts around these wires 20, 22, and thus the laser pulse then also reaches the qubits 14, 16 for formatting.

[0083] Then the qubits 14, 16 can be addressed individually or jointly. For this purpose, a suitable high-frequency current in the kilohertz range is applied to the contact portions 26 of the corresponding wires 20, 22 to address the nuclear spins of the qubits 14, 16. The currents flowing in the wires 20, 22 respectively induce magnetic fields acting on the corresponding qubits 14, 16.

[0084] Here, a near magnetic field is formed around the wires 20, 22. Due to the Laplace equation, this near magnetic field increases in the regions of the qubits 14, 16 arranged adjacent to each other respectively, and thus particularly well affects the nuclear spins of these qubits 14, 16.

[0085] Therefore, an appropriate near magnetic field is provided to each qubit 14, 16, thereby addressing it. At the same time, an anti-magnetic field is provided to the other qubits 16, 14 respectively, and this anti-magnetic field compensates the magnetic field components of the near magnetic field used to address the qubits 14, 16 at the positions of the other qubits 16, 14 respectively, so crosstalk cannot occur.

[0086] Therefore, not only can two qubits 14, 16 be addressed differently or identically simultaneously, but also only a single qubit 14, 16 can be addressed independently of the addressing of the other qubit 14, 16.

[0087] In order to read out the qubits 14, 16, for example, suitable uniform laser radiation can be carried out again, so as to generate photoelectrons in the two qubits 14, 16, and then the photoelectrons are intercepted and measured through the respectively associated first wires 20, 22, while the second wire 24 is used as a ground part. For this purpose, there is a changeover switch so that the wires 20, 22 can be used once for formatting (i.e., supplying current) and once for reading out (i.e., measuring current).

[0088] Alternatively, suitable laser pulses can also be fed to each qubit 14, 16 respectively through a suitable lighting device, so that the qubits 14, 16 can be read out individually.

[0089] The device 10 can be manufactured, for example, according to the following steps: According to DE 10 2019 117423.6, the qubits 14, 16 are manufactured by doping diamond 12 and subsequent first and second tempering steps, wherein the steps of contacting the second wire 24 and shielding and contacting the first wires 20, 22 are appropriately integrated into this manufacturing method.

[0090] More precisely, the diamond 12 is doped with sulfur or another suitable dopant and a first tempering step is carried out at about 1000 °C. Then, for example, through a removable mask, the second wire 24 made of tungsten together with the corresponding contact surface 26 is vapor deposited on the surface 18 of the diamond 12.

[0091] Then, a contact mask made of glass or silicon carbide (not shown in Figure 1 for clarity) is arranged on the surface 18 of the diamond 12 provided with the second wire 24 and having two openings, and these two openings have the shape of the first wires 20, 22 and they are arranged at a desired distance from the second wire 24.

[0092] The corresponding mask manufacturing method is familiar to those skilled in the art, so it does not have to be discussed in more detail.

[0093] Nitrogen implantation is carried out through this mask to generate the qubits 14, 16. Thus, the positions of the qubits 14, 16 under the subsequently formed first wires 20, 22 are also precisely predetermined.

[0094] After a second tempering step at about 800 °C, the first wires 20, 22 made of ITO and the corresponding contact surfaces 26 are vapor deposited together through the mask, thus completing the device 10.

[0095] In Figure 3 and Figure 4 a second preferred embodiment of the device 50 according to the present invention is shown in more detail.

[0096] InFigure 3 and Figure 4 As can be seen from Figure 4 , the device 50 has a diamond layer material 52, in which nine qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 are arranged at a depth of approximately 10 nm below the surface 72 of the diamond material 52.

[0097] Directly above the nine qubits 54, 56, 58, 60, 62, 64, 66, 68, 70, three first conductive wires 74, 76, 78 made of ITO are arranged in the first layer 80. These first wires 74, 76, 78 are covered by an insulating layer 82, which can be formed, for example, of an oxide, in particular of SiO2. On the surface 84 of the insulating layer 82, another three first conductive wires 86, 88, 90 are arranged in the second layer 92.

[0098] The wires 74, 76, 78 in the first layer 80 are aligned parallel to each other in a plane, and the wires 86, 88, 90 in the second layer 92 are aligned parallel to each other in a plane. The wires 74, 76, 78 of the first layer 80 are perpendicularly aligned with the wires 86, 88, 90 of the second layer 92, and all the wires are electrically insulated from each other. For simplicity of illustration, the corresponding contact surfaces are not shown here. These first conductive wires 74, 76, 78, 86, 88, 90 also have a height and width in the range of 1 nm to 10 nm, preferably a height and width of 5 nm. The lengths of the straight portions of the wires 74, 76, 78, 86, 88, 90 extend beyond the outer qubits 54, 56, 58, 60, 64, 66, 68, 70 by approximately 5 nm to 10 nm, respectively.

[0099] These first conductive wires 74, 76, 78, 86, 88, 90 are used for addressing and reading out the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 and have a spacing of approximately 20 nm to 30 nm in the respective layers 80, 92, which thus corresponds to the spacing of the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 directly below the virtual intersection points of the wires 74, 76, 78, 86, 88, 90 (see Figure 4 ). Due to the distance of 20 nm to 30 nm, the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 are easily entangled.

[0100] Instead (as in accordance with Figure 1 and 2one or more second conductive wires in the device 10, where there is a common back contact 94, for example made of tungsten, which is located between the diamond layer 52 and the substrate 96. The back contact 94 serves as a common ground for reading out the individual qubits 54, 56, 58, 60, 62, 64, 66, 68, 70.

[0101] The device 50 now operates as follows: The qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 are simultaneously formatted by a suitable laser pulse passing through the surface 84, and this laser pulse can easily reach the qubits 14, 16 through the transparent wires 74, 76, 78, 86, 88, 90 made of ITO.

[0102] Now, the individual qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 can be addressed by respectively assigning two first wires 74, 76, 78, 86, 88, 90 to each qubit 54, 56, 58, 60, 62, 64, 66, 68, 70. Thus, through different suitable signals on the respectively crossed first wires 74, 76, 78, 86, 88, 90, each individual qubit 54, 56, 58, 60, 62, 64, 66, 68, 70 can be individually addressed by a separately formed near magnetic field. More precisely, the projections of the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 on the layers 80, 92 are located near the intersections of the first wires 74, 76, 78, 86, 88, 90, such that the high-frequency magnetic fields applied in the crossed wires 74, 76, 78, 86, 88, 90 are superimposed on each other, thereby establishing a separate near magnetic field for each qubit 54, 56, 58, 60, 62, 64, 66, 68, 70. By means of a separately adapted anti-magnetic field in these separate near fields, the influence of the near magnetic field of the corresponding remaining qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 is eliminated or sufficiently reduced here.

[0103] Therefore, the crossed wires 74, 76, 78, 86, 88, 90 can generate an elliptical or circularly polarized near magnetic field for each qubit 54, 56, 58, 60, 62, 64, 66, 68, 70, and thus a Qutrit state can be generated.

[0104] For example, in order to read out qubits 54, 56, 58, 60, 62, 64, 66, 68, 70, suitable laser pulses are used, wherein the first wires 74, 76, 78, 86, 88, 90 are switched from current supply to current measurement, and the back contact is used as the ground for the generated photoelectrons. By combining the respective measurement signals of the first wires 74, 76, 78, 86, 88, 90, each qubit 54, 56, 58, 60, 62, 64, 66, 68, 70 can have its specific measurement signal.

[0105] The device 50 can be manufactured, for example, according to the following steps: According to DE 10 2019 117 423.6, the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 are manufactured by doping the diamond layer material 52 and subsequent first and second annealing steps, wherein the steps of contacting the back contact 94 and contacting the first wires 74, 76, 78, 86, 88, 90 are appropriately integrated into the manufacturing method.

[0106] More precisely, the back contact 94 made of tungsten is produced here by deposition (e.g., sputtering) on a suitable substrate material 96, and the diamond layer 52 is arranged thereon, for example, by chemical vapor deposition. According to DE 10 2019 117423.6, the diamond layer 52 is doped with sulfur or another dopant and undergoes a first annealing step at approximately 1000 °C.

[0107] Then nitrogen is implanted to produce the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70, wherein the nitrogen is implanted with an AFM probe for precise positioning of the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70. This method is described, for example, substantially in the article "Nanoscale Engineering and Optical Addressing of Single Spins in Diamond" by S. Pezzagna et al., Small 2010, 6, 19, 2117 - 2121. For orientation, auxiliary markers in the form of graphite markings or metal wires can be arranged outside the surface area where the qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 will be provided.

[0108] After a second tempering step at approximately 800 °C, a first wire 74, 76, 78, for example made of silver, of layer 80 is drawn on the surface 72 of the diamond material 52 by means of an AFM probe, and a corresponding contact surface (not shown) is produced. Then, a suitable electrically insulating layer 82, for example made of SiO2, is arranged on the surface 72 of the diamond material 52, thus covering the first wires 74, 76, 78. Finally, the first wires 86, 88, 90 of the second layer 92 are also arranged on the surface 84 of the insulating layer 82 by drawing with an AFM probe.

[0109] Here, the wire drawing using the AFM probe can be carried out according to the method substantially described in the publication by I. W. Rangelow et al., “Atomic force microscope integrated with a scanning electron microscope for correlative nanofabrication and microscopy”, J. Vac. Sci. Technol. B 36(6), November / December 2018. In addition, markers or auxiliary lines can also be used for orientation.

[0110] As an alternative to wire drawing using the AFM probe, a mask-based method can also be used to produce the first wires 74, 76, 78, 86, 88, 90, wherein preferably these masks are removed each time to ensure that the distance between the wires 74, 76, 78, 86, 88, 90 and the respective associated qubits 54, 56, 58, 60, 62, 64, 66, 68, 70 is as small as possible.

[0111] It can be clearly seen from the above description that the present invention enables the qubits 14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70 to be addressed in a simple manner and method, without the risk of crosstalk between different qubits 14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70. Here, for the different qubits 14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70, they can be addressed individually or jointly. In addition, the qubits 14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70 can also be easily read out.

[0112] Unless otherwise specified, all features of the present invention can be freely combined with each other. In addition, unless otherwise specified, the features described in the description of the drawings can be freely combined with other features as features of the present invention. Here, the individual features of the exemplary embodiments are not explicitly restricted to combinations with other features of the exemplary embodiments. In addition, the physical features of the device can also be deformed and used as method features, and the method features can also be deformed and used as the physical features of the device. Therefore, such deformations are automatically disclosed.

[0113] List of Reference Numerals

[0114] 10 First preferred embodiment of the device according to the present invention

[0115] 12 Diamond bulk material

[0116] 14, 16 Qubits

[0117] 18 Surface of the diamond material 12

[0118] 20, 22 First conductive wires made of ITO (indium tin oxide)

[0119] 24 Second conductive wire made of tungsten

[0120] 26 Contact surfaces of the wires 20, 22, 24

[0121] 50 Second preferred embodiment of the device according to the present invention

[0122] 52 Diamond layer material

[0123] 54, 56, 58 Qubits

[0124] 60, 62, 64 Qubits

[0125] 66, 68, 70 Qubits

[0126] 72 Surface of the diamond material 52

[0127] 74, 76, 78 First conductive wires made of ITO (indium tin oxide)

[0128] 80 First layer in which the wires 74, 76, 78 are arranged

[0129] 82 Insulating layer

[0130] 84 Surface of the insulating layer 82

[0131] 86, 88, 90 First conductive wires made of ITO (indium tin oxide)

[0132] 92 Second layer in which the wires 86, 88, 90 are arranged

[0133] 94 Back contact made of tungsten

[0134] 96 Substrate

Claims

1. A method for addressing at least one qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) in a group of more than two qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70), It is characterized in that The individual qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) to be addressed is exposed to an electromagnetic field, while at least one other qubit in the group of qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) is exposed to a reverse electromagnetic field, such that the electromagnetic field has no effect on the other qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70), or the effect of the electromagnetic field on the other qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) is different from the effect on the qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) to be addressed, and amplitude modulation is performed on the electromagnetic field and the reverse electromagnetic field, and there is a temporal variation between the modulation of the electromagnetic field and the modulation of the reverse electromagnetic field.

2. The method according to claim 1, characterized in that, Color centers in diamond (12, 52) are used as the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70).

3. The method according to claim 2, wherein The color center is an NV center.

4. The method according to any one of claims 1 to 3, characterized in that An electromagnetic near field is used as the electromagnetic field and the reverse electromagnetic field.

5. The method according to claim 4, wherein The electromagnetic near field is a magnetic near field.

6. The method according to claim 5, wherein The electromagnetic near field is a magnetic near field having a frequency in the microwave range and / or the kilohertz range.

7. The method according to any one of claims 1 to 3, characterized in that, The electromagnetic field and the reverse electromagnetic field are provided by electromagnetic sources (20, 22; 74, 76, 78, 86, 88, 90), wherein the size of the electromagnetic sources (20, 22; 74, 76, 78, 86, 88, 90) is smaller than the distance between adjacent qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70).

8. The method according to claim 7, wherein The electromagnetic source is a conductive structure.

9. The method according to claim 8, characterized in that, The electromagnetic source is a line, a metallized structure, or a wire (20, 22; 74, 76, 78, 86, 88, 90).

10. The method according to any one of claims 1 to 3, characterized in that, The qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) are composed of a transparent material (12; 52), such that the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) can be formatted by optical radiation.

11. The method according to claim 10, wherein The qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) are formatted by laser radiation.

12. The method according to claim 11, characterized in that, Multiple of the qubits are formatted simultaneously.

13. The method according to claim 12, wherein All of the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) are formatted simultaneously.

14. An apparatus for addressing at least one qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) in a set of more than two qubits, It is characterized in that, the apparatus comprising means (20, 22; 74, 76, 78, 86, 88, 90) for generating an electromagnetic field, the means for generating the electromagnetic field being designed such that an individual qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) to be addressed can be exposed to the electromagnetic field, and the apparatus comprising means (20, 22; 74, 76, 78, 86, 88, 90) for generating at least one reverse electromagnetic field, the means for generating the at least one reverse electromagnetic field being designed such that at least one other qubit in the set of qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) can be exposed to the reverse electromagnetic field, such that the electromagnetic field has no effect on the other qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70), or the effect of the electromagnetic field on the other qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) is different from the effect on the qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) to be addressed, and amplitude modulating the electromagnetic field and the reverse electromagnetic field, and there being a temporal variation between the modulation of the electromagnetic field and the modulation of the reverse electromagnetic field.

15. The device according to claim 14, characterized in that, The apparatus is adapted to perform the method according to any one of claims 1 to 13.

16. The device according to claim 14 or 15, characterized in that, The apparatus comprises an electromagnetic source (20, 22; 74, 76, 78, 86, 88, 90) for generating the electromagnetic field and the reverse electromagnetic field, wherein each qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) is assigned at least one of the electromagnetic sources.

17. The device according to claim 16, characterized in that, The electromagnetic source is a first conductive structure.

18. The device according to claim 17, wherein The electromagnetic source is a line, a wire (20, 22; 74, 76, 78, 86, 88, 90) or a metallized structure.

19. The device according to claim 16, characterized in that, A plurality of the electromagnetic sources (20, 22; 74, 76, 78, 86, 88, 90) are arranged in a layer, wherein the distance of the qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) from its respective associated electromagnetic source in a direction perpendicular to the layer is at most 30 nm, and / or wherein the distance of the qubit (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) projected onto the layer from its respective associated electromagnetic source (20, 22; 74, 76, 78, 86, 88, 90) is at most 20 nm.

20. The device according to claim 19, wherein Among them, the distance of the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) from their respective associated electromagnetic sources in a direction perpendicular to the layer is at most 20 nm, and / or wherein the distance of the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) projected onto the layer from their respective associated electromagnetic sources (20, 22; 74, 76, 78, 86, 88, 90) is at most 10 nm.

21. The device according to claim 20, wherein Among them, the distance of the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) from their respective associated electromagnetic sources in a direction perpendicular to the layer is in the range of 0 nm to 10 nm, and / or wherein the distance of the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) projected onto the layer from their respective associated electromagnetic sources (20, 22; 74, 76, 78, 86, 88, 90) is in the range of 0 nm to 5 nm.

22. The device according to claim 17, wherein At least one of the first conductive structures (20, 22; 74, 76, 78, 86, 88, 90) can be connected to an electromagnetic exciter and a photoelectron detector.

23. The device according to claim 17, characterized in that, The device includes at least one second conductive structure (24; 94), and the second conductive structure forms a ground portion for reading out the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70).

24. The device according to claim 23, characterized in that, The second conductive structure is a second conductive wire (24).

25. The device according to claim 24, wherein, The second conductive structure is a circuit or a metallization structure or an electrode (94).

26. The device according to claim 25, wherein The second conductive structure (24) is arranged adjacent to the first electromagnetic source (20, 22).

27. The device according to claim 26, characterized in that, The second conductive structure (24) is arranged to be at most 40 nm apart from the first electromagnetic source (20, 22) in the layer.

28. The device according to claim 27, characterized in that, The second conductive structure (24) is arranged to be 30 nm apart from the first electromagnetic source (20, 22) in the layer.

29. The device according to claim 28, wherein, The second conductive structure (24) is arranged to be in the range of 10 nm to 20 nm apart from the first electromagnetic source (20, 22) in the layer.

30. The device according to claim 23, characterized in that, The i) cross-section of the first conductive structure (20, 22; 74, 76, 78, 86, 88, 90) and / or the second conductive structure (24) has a longitudinal dimension less than 50 nm, and / or ii) length is less than 50 nm.

31. The device according to claim 30, wherein, The i) cross-section of the first conductive structure (20, 22; 74, 76, 78, 86, 88, 90) and / or the second conductive structure (24) has a longitudinal dimension less than 20 nm, and / or ii) length is less than 30 nm.

32. The device according to claim 31, characterized in that, The i) cross-section of the first conductive structure (20, 22; 74, 76, 78, 86, 88, 90) and / or the second conductive structure (24) has a longitudinal dimension in the range of 1 nm to 10 nm, and / or ii) with a length of 5 nm to 20 nm.

33. The device according to claim 14 or 15, characterized in that, The qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) are arranged in a one-dimensional, two-dimensional or three-dimensional manner, and / or the components (20, 22; 74, 76, 78, 86, 88, 90) for generating an electromagnetic field are arranged in a one-dimensional, two-dimensional or three-dimensional manner.

34. The device according to claim 33, characterized in that, The device includes more than two layers (80, 92).

35. The device according to claim 34, characterized in that, The conductive structures (74, 76, 78, 86, 88, 90) are arranged parallel to each other in the layers, wherein the conductive structures (74, 76, 78, 86, 88, 90) of different said layers (80) are arranged differently.

36. The device according to claim 35, wherein An electrical insulator (82) is arranged between the two layers (80, 92).

37. A method for manufacturing a device according to any one of claims 14 to 36, characterized in that, More than two qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70) are generated in the surrounding material, and a first conductive wire (20, 22; 74, 76, 78, 86, 88, 90) is arranged on the surrounding material.

38. The method according to claim 37, wherein At least one of the following steps is also performed: - Selecting a diamond layer (12; 52) as the surrounding material, - Doping the surrounding material with a dopant, - Performing a first tempering step after the doping, - Performing a second tempering step after generating the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70), - Laying a second conductive wire (24) for reading out the qubits (14, 16; 54, 56, 58, 60, 62, 64, 66, 68, 70).

39. The method according to claim 38, wherein The dopant is sulfur, phosphorus or oxygen.

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