Spin information transport device and method for its manufacture

Abstract

The present invention relates to a spin information transport device 1, which comprises a diamond matrix 3 made of C12 diamond and two defect centers 4, in particular NV centers, within the diamond matrix 3, wherein a spin polarization channel 6, which is formed of C13 enriched diamond, extends to enable a directed propagation of spin polarization between the two defect centers 4. A further object of the invention is a method for manufacturing such a spin information transport device 1.

Description

[0001] The present invention relates to a spin information transport device comprising a diamond matrix made of C12 diamond and two defect centers, in particular NV centers, within the diamond matrix. A further aspect of the invention is a method for manufacturing such a spin information transport device.

[0002] US 9,317,473 B2 describes a quantum information processor (QIP) that can comprise a plurality of quantum registers, each containing at least one nuclear spin and at least one localized electron spin. Some of the quantum registers can be coherently coupled via a dark spin chain, which consists of a series of optically unaddressable spins. Each quantum register can be optically addressable, allowing quantum information in each register to be optically initialized and read out and transferred between registers via the dark spin chain, either by adiabatic sequential swap or by free fermion state transfer.A scalable architecture for the QIP can include an array of super-plaquettes, where each super-plaquette consists of a grid of individually optically addressable plaques coupled to each other via dark spin chains and separately controllable by limited microwave fields to enable parallel operations.

[0003] LÓPEZ, GV. Diamond as a solid-state quantum computer with a linear chain of nuclear spins system. arXiv preprint arXiv:1310.0750, 2013 describes: By removing a C12 atom from the tetrahedral configuration of diamond, replacing it with a C13 atom, and repeating this in a linear direction, it is possible to create a linear chain of nuclear spins and build a solid-state quantum computer. Qubit rotation and controlled-non-quantum (CNOT) quantum gates are immediately derived from this configuration, and the CNOT quantum gate is used to determine the design parameters of this quantum computer.

[0004] DE 10 2023 206 516 B3 describes a diamond element comprising a substrate with an epitaxial layer system of carbon isotope-enriched diamond material applied thereon, wherein the layer system has at least two superimposed spin layers, each with a spin species, and wherein a substantially spin-free buffer layer is arranged between each of the two spin layers.

[0005] UNDEN, Thomas, et al. Coherent control of solid state nuclear spin nano-ensembles. npj Quantum Information, 2018, Vol. 4, No. 1, p. 39 describes: The detection and control of nuclear spin nano-ensembles is crucial for the further development of nuclear magnetic resonance (NMR) spectroscopy and for emerging solid-state quantum technology. Here, the fabrication of an a-≈1 nanometer thick diamond layer is presented, consisting of C13 nuclear spins doped with nitrogen vacuum centers (NVs) and embedded in a spin-free C12 crystal matrix. A single NV near the layer is used to polarize the C13 spins and read out their magnetization. A method for the coherent control of several dozen nuclear spins using radio frequency pulses is presented, and the basic coherent control experiments, Rabi oscillations and Ramsey spectroscopy, are shown, whereby any NMR pulse sequence can be implemented.The results shown here represent an important step towards the realization of a nuclear spin-based quantum simulator.

[0006] The production of synthetic diamonds using CVD (chemical vapor deposition) is a common industrial technique. The focus is primarily on growing diamond layers with a thickness exceeding 100 nm, which are mainly used in the jewelry industry and for material processing, such as cutting tools. In these applications, only the mechanical properties of the resulting diamonds, such as hardness, are relevant.

[0007] Synthetic diamonds have recently gained increasing relevance for high-tech applications, such as in quantum technology and semiconductor technology. In quantum technology, diamond is used as a matrix into which atomic defect centers are introduced, such as NV (nitrogen defect centers), SiV (silicon defect centers), GeV (germanium defect centers), or SnV (tin defect centers).

[0008] To make the defect centers usable for quantum computing, for example, they are introduced into a matrix enriched with the isotope carbon-13 (C13), which, unlike the isotope carbon-12 (C12), has a non-zero nuclear spin. If the distance between a defect center and a C13 atom is small enough, a measurable coupling occurs between the spins of the defect center and the C13 atom, so that they can be used as qubits.

[0009] The defect centers are located in the layer of C13-enriched diamond. Provided this layer has a sufficient density of C13 atoms and thus of C13 nuclear spins, the spin polarization can propagate in any direction throughout the entire diamond layer. However, directed propagation of spin polarizations, which are generated as spin information through quantum manipulation of the defect centers, is therefore not possible with these diamond structures. Such directed propagation would be necessary for the creation of more complex quantum mechanical circuit elements.

[0010] The object of the present invention is therefore to provide a device from which more complex quantum mechanical circuit elements can also be constructed.

[0011] In a device of the type mentioned above, this problem is solved by a spin polarization channel formed from C13 enriched diamond to enable a directed propagation of spin polarization, which extends between the two defect centers, in particular connecting the two defect centers.

[0012] A spin polarization channel enables directed polarization diffusion between atomic defect centers. The spin polarization channel, particularly one made of C13-enriched synthetic diamond, can essentially restrict the propagation of spin polarization to a one-dimensional direction. In this way, the one-dimensional diffusion of the (nuclear) spin polarization can occur directed along the longitudinal axis of the spin polarization channel.

[0013] The diamond matrix, especially synthetic diamond matrix made from C12 diamond, can provide a nuclear spin-free layer in which spin polarization cannot propagate, so that the spin polarization channel in the diamond matrix cannot be bypassed.

[0014] The spin polarization channel enables the spin information transport device to transport quantum information from one defect center to another. In particular, the use of multiple spin information transport devices opens up the possibility of constructing more complex quantum mechanical circuit elements and, for example, creating quantum transistors and coherently connecting them to form a network, a qubit register.

[0015] The spin polarization channel can exhibit a very high enrichment of C13. In particular, enrichments of C13 in the range of 10% to 99.99%, preferably in the range of 50% to 99.99%, are possible. Such a high enrichment of C13 ensures efficient polarization diffusion, i.e., spin transport, within the spin polarization channel.

[0016] The atomic vacancy centers can be NV centers (nitrogen vacancy centers), SiV centers (silicon vacancy centers), GeV centers (germanium vacancy centers) and / or SnV centers (tin vacancy centers).

[0017] Preferably, the spin polarization channel is arranged above the defect centers. By arranging the spin polarization channel above the defect centers, the directed propagation of the spin polarization can occur in a different plane than the generation of the spin polarization by quantum manipulation of the defect centers. In particular, the directed propagation of the spin polarization can occur in a layer with a different chemical composition than the layer in which the defect centers are arranged.

[0018] "Above" refers to an arrangement on the side of the defect centers facing away from the interior of the diamond matrix, and in particular away from a substrate. More generally, "above" can refer to an arrangement along a growth direction.

[0019] The spin polarization channel can be arranged above the defect centers in such a way that a defect center is located below each diametrically opposite end of the spin polarization channel.

[0020] It is further advantageous if the spin polarization channel is covered by a C12 diamond protective layer. With this C12 diamond protective layer, particularly a pure one, the spin polarization channel can be protected on the side facing away from the diamond matrix. By using the non-spin C12 in the diamond protective layer, spin shielding of the spin polarization channel towards the outside of the device can be achieved to protect against spin noise. The C12 diamond protective layer can, in particular, have a thickness of at least 50 nm, preferably at least 100 nm.

[0021] According to one design, the diamond matrix is ​​arranged on a diamond substrate. The diamond substrate can form a mechanically and chemically stable substrate for the diamond matrix. The diamond matrix can be chemically bonded to the diamond substrate, in particular grown on it.

[0022] It is possible for the two defect centers to be separated by 5 nm to 100 µm, and in particular by 500 nm to 1 µm. In this way, spin polarization can be transferred between two points that are far apart for quantum mechanical applications.

[0023] Furthermore, the spin polarization channel may have a width of 1 nm to 10 µm, preferably in the range of 5 nm to 100 nm, and / or a length of at least 5 nm, preferably at least 500 nm, particularly preferably in the range of 500 nm to 1 µm, and more preferably in the range of 1 µm to 5 µm, and / or a thickness in the range of 0.5 nm to 100 nm, preferably 1 nm to 10 nm. With a spin polarization channel of this length, spin polarization can be directed over a considerable distance for quantum mechanical applications. With a spin polarization channel of this width and / or thickness, measured transversely to the plane of the diamond matrix, the propagation possibilities of the spin polarization within the spin polarization channel can be easily restricted to one-dimensional propagation along the length of the spin polarization channel.

[0024] It can be further advantageous if the diamond matrix has a thickness of at least 50 nm, and particularly at least 100 nm. In this way, the diamond matrix can provide a mechanically stable layer for receiving the defect centers.

[0025] In a method of the type mentioned above, it is proposed to solve the aforementioned problem by comprising the steps of growing a diamond matrix of C12 enriched diamond onto a, in particular ultrapure, diamond substrate by means of CVD, introducing defect centers into the diamond matrix, growing a C13 enriched diamond layer and selectively removing the C13 enriched diamond layer, in particular by etching, to form a spin polarization channel.

[0026] Using this method, a spin information transport device according to the invention can be produced, comprising a spin polarization channel that enables directed polarization diffusion between the defect centers. The features described in connection with the spin information transport device according to the invention can also be applied individually or in combination to this method. The same advantages arise as already described.

[0027] In particular, by growing a diamond matrix of C12-enriched diamond onto an ultrapure diamond substrate using CVD, the unwanted introduction of foreign atoms, i.e., non-carbon atoms, from the diamond substrate into the diamond matrix during further processing steps can be prevented. An ultrapure diamond substrate can exhibit a residual nitrogen concentration of less than 5 ppb (parts per billion) remaining from the production of the diamond substrate.

[0028] The diamond matrix can have a thickness, measured along its growth direction on the diamond substrate, of at least 50 µm, in particular at least 100 µm.

[0029] By growing the diamond using CVD, a diamond matrix enriched with 12C, and specifically consisting of C12, can be easily created on the diamond substrate. This C12-enriched diamond matrix can provide a nuclear spin-free layer into which the defect centers can be placed. This prevents spin polarization propagation within the diamond matrix and thus avoids bypassing the spin polarization channel.

[0030] C12-enriched methane gas can be used to grow the diamond matrix using CVD.

[0031] To introduce defect centers, ion implantation into the diamond matrix can be performed. During ion implantation, ions, e.g., nitrogen ions in the case of NV centers, can be accelerated onto the diamond matrix. The ions can come to rest at a depth within the diamond matrix that depends on the acceleration energy, creating defects along their path. A subsequent heating process allows the ions and defects to combine to form defect centers, e.g., in the case of ion-implemented nitrogen, to form NV centers. Ion implantation can be carried out, in particular, using nitrogen-15 ions (15N+) with an energy of 0.1 keV to 5 keV, preferably 1 keV, and / or a dose of at least 10 11 15N+ / cm.

[0032] Ion implantation can be controlled, in particular by using a mask that covers the diamond matrix and allows ion implantation only in some predefined areas of the diamond matrix.

[0033] Ion implantation can be performed in such a way that the defect centers are created below the predetermined ends of the spin polarization channel.

[0034] By growing a C13-enriched diamond layer, a diamond layer containing C13 nuclear spins can be produced on a diamond matrix, particularly one free of C13 nuclear spins. The C13-enriched diamond layer can contain C12 in addition to C13, and in particular, can consist predominantly of C12. The C13-enriched diamond layer can be grown, especially directly, on the diamond matrix. The C13-enriched diamond layer can have a thickness in the range of 0.5 nm to 100 nm, preferably 1 nm to 10 nm. A very low growth rate, below the normally used growth rates, can be employed during the growth of the diamond layer to allow for nm-precise adjustment of the layer thickness.

[0035] By selectively removing the C13-enriched diamond layer, the spin polarization channel can be easily formed without altering the diamond matrix. This selective removal can be achieved by completely removing the C13-enriched diamond layer in specific areas, particularly those not forming a spin polarization channel. Etching is a particularly effective method for selectively removing the C13-enriched diamond layer. A lithographic etching process can be used for this purpose. In this process, the area of ​​the diamond layer intended to form the spin polarization channel can be masked off, so that only the areas of the C13-enriched diamond layer not covered by the mask are etched away. The mask can be applied to the C13-enriched diamond layer as a photoresist.Subsequently, the diamond layer, which is coated in certain areas with the photoresist and enriched with C13, can be exposed, thus enabling selective etching.

[0036] It can be provided that a C12 diamond protective layer is grown on the spin polarization channel to increase the coherence time of the defect centers. The C12 diamond protective layer can shield the spin polarization channel from negative influences from the surface of the spin information transport device. The C12 diamond protective layer can be ultra-pure, i.e., exhibiting a C12 enrichment of essentially 99.9%, and in particular, C13-free. By using the non-spin-free C12 in the diamond protective layer, spin shielding of the spin polarization channel from the outside of the device can be achieved, thus protecting against spin noise.

[0037] The C12 diamond protective layer can be grown in a thickness of at least 50 nm, preferably at least 100 nm.

[0038] Advantageously, the growth of the C13-enriched diamond layer can be achieved using CVD with C13-enriched methane gas. The enrichment of the diamond layer with C13 can be easily accomplished by growing the diamond with C13-enriched growth gas, particularly methane gas. The density of the C13 nuclear spins in the grown synthetic diamond layer can be adjusted by controlling the degree of C13 enrichment of the growth gas.

[0039] Furthermore, it can be advantageous to introduce defect centers into the diamond matrix by ion implantation followed by high-temperature bake-out, particularly in a vacuum. Through ion implantation and subsequent high-temperature bake-out, ions can be introduced into the diamond matrix and then bond with the defects during the bake-out process to form defect centers. The high-temperature bake-out can be carried out, in particular, at a temperature of 1000 °C for 3 hours in a vacuum, preferably at a pressure below 10 -7 mbar.

[0040] Preferably, the C13-enriched diamond layer is selectively removed by controlled plasma etching, in particular ICP, of the surface of the C13-enriched diamond layer. Controlled plasma etching allows diamond material to be removed from the surface of the C13-enriched diamond layer with nanometer-level accuracy. Controlled plasma etching can be achieved by inductive plasma etching (ICP) or reactive ion etching (RIE). Inductive plasma etching can be achieved by igniting an inductively coupled plasma, in particular an oxygen plasma or an Ar / SF6 plasma (SF6: sulfur hexafluoride), and applying an accelerating voltage that accelerates the reactive ions onto the diamond layer.

[0041] Further details and advantages of a spin information transport device and a method according to the invention will be explained below by way of example using an embodiment of the invention schematically illustrated in the figure. This figure shows: Fig. 1a-f The individual steps of a manufacturing process according to the invention as well as a spin information transport device according to the invention.

[0042] To better illustrate the individual layers, these are shown in the subfigures ( Fig. 1a to 1f) are shown spaced apart from each other. However, in the spin information transport device 1 and during its manufacture, these layers lie so close together that they connect to each other in the growth direction W.

[0043] In Fig. Figure 1a shows the first step in the fabrication of the spin information transport device 1. A diamond matrix 3 is grown on a pure diamond substrate 2 using CVD. During CVD growth, a C12-containing growth gas 8 is used. This growth gas 8 is C13-free for the growth of the diamond matrix 3, so that the diamond matrix 3 is spinless after growth is complete. Methane gas can be used as the growth gas 8.

[0044] Along the growth direction W, a diamond matrix 3 is thus formed on the diamond substrate 2. This diamond matrix 3 has a thickness M of at least 50 nm to 100 nm. It is therefore thick enough to accommodate the defect centers 4 introduced in the subsequent step without them penetrating into the diamond substrate 2.

[0045] After the diamond matrix 3 has grown, the defect centers 4 are introduced into the diamond matrix 3, as described in Fig. 1b shown.

[0046] To introduce the defect centers 4 into the diamond matrix 3, an ion implantation is first performed. For this, for example, nitrogen-15 ions (15N+) with an energy of 1 keV and a dose of 10 11 The ions are accelerated to 15 N / cm² onto the diamond matrix 3. At a depth dependent on the acceleration energy, the ions then come to rest within the diamond matrix 3. On their way to this resting position, the ions create defects in the diamond matrix 3 as they traverse the material.

[0047] To introduce the ions precisely into the diamond matrix 3, it is first masked. This masking process leaves only those areas on the surface of the diamond matrix 3 exposed where the defect centers 4 will later be located. The areas left unmasked during ion implantation can, for example, have distances of approximately 5 nm to 100 µm from each other, so that two defect centers 4 in the subsequent spin information transport device 1 are arranged at a distance of approximately 5 nm to 100 µm from each other.

[0048] Following ion implantation, the system consisting of diamond substrate 2 and diamond matrix 3 undergoes high-temperature bake-out. This high-temperature bake-out is performed at a pressure below 10 -7mbar in a vacuum to prevent unwanted chemical reactions. The system is then heated to a temperature exceeding 1000 °C for three hours. At these temperatures, the ions and defects implemented in the diamond matrix 3 can combine to form defect centers 4. For example, nitrogen-15 ions are implanted into the diamond matrix 3 as defect centers 4 by subsequent high-temperature baking.

[0049] These defect centers 4 are indicated in the figure as pairs of points, symbolizing the connection between the implemented ions and defects. The arrows of these pairs symbolize the non-zero spins of the defect centers 4, with which they can couple to the spin polarization channel 6 formed below.

[0050] In Fig. 1c and Fig. Figure 1d shows the growth of a C13-enriched diamond layer 5 after the introduction of the defect centers 4. The diamond layer 5 is also grown using CVD and has a thickness D of approximately 1 nm after growth.

[0051] Similar to the growth of the diamond matrix 3, a C12-containing gas, in particular methane gas, is used as the growth gas. However, this growth gas is enriched with C13. Therefore, the diamond layer 5 grown on the diamond matrix 3 is also enriched with C13. This makes it possible to subsequently fabricate a spin polarization channel 6, which is arranged above the defect centers 4.

[0052] By enriching the diamond layer 5 with C13, it contains C13 atoms that exhibit a non-zero nuclear spin. These C13 atoms thus contrast with the other spinless (i.e., zero) C12 atoms of the diamond layer 5. With this nuclear spin, the C13 atoms can couple to the spins of the defect centers 4, thereby enabling the transport of spin polarization. The C13 atoms with this nuclear spin are in Fig. 1d are indicated as points with arrows, which symbolize the nuclear spins.

[0053] It can also be seen that the diamond matrix 3 located beneath the diamond layer 5 largely lacks diamond atoms with nuclear spin, as it comprises the spin-less C12 atoms. Only the defect centers 4 in the diamond layer 5 exhibit nuclear spin. Therefore, propagation of spin polarization from the defect centers 4 into the diamond matrix 3 is not possible.

[0054] However, in the C13-enriched diamond layer 5, spin polarization can propagate in all directions. With the in Fig. 1c and Fig. In the diamond layer 5 shown in 1d, a directed propagation of spin polarization cannot yet be achieved.

[0055] To enable directed propagation of spin polarization, a spin polarization channel 6 must be formed from the diamond layer 5, as shown in Fig. 1e shown. In this process, the C13 enriched diamond layer 5 is partially removed, leaving only the spin polarization channel 6.

[0056] For this purpose, a lithographic ICP etching process is used. The area of ​​the diamond layer 5 that is to form the spin polarization channel 6 is coated with a photoresist. The diamond layer 5, thus masked, can be exposed to the plasma 9. In the unmasked areas, the C13-enriched diamond layer 5 is thereby ablated in a controlled manner.

[0057] After ablation, only a long and thin spin polarization channel 6 of C13-enriched diamond remains from the C13-enriched diamond layer 5. In the illustrated embodiment, this spin polarization channel 6 has a width B in the range of 5 nm to 100 nm, a length L in the range of approximately 5 nm to 100 µm, and a thickness D in the range of 0.5 nm to 100 nm after forming.

[0058] The spin polarization channel 6 also contains C13 atoms with nuclear spin. Since the spin polarization channel 6 is located above and between the defect centers 4, it enables a directed propagation of spin polarization between the two defect centers 4.

[0059] Although the fabrication of a single spin polarization channel 6 has been described above, several spin polarization channels 6 can also be fabricated in parallel between different defect centers 4 of the diamond matrix 3. In this way, a spin information transport device 1 with multiple spin polarization channels 6 on the same diamond matrix 3 can be created, for example, to obtain quantum transistors or qubit registers.

[0060] In Fig. Figure 1f shows how the spin information transport device 1 is additionally provided with a C12 diamond protective layer 7 after the formation of the spin polarization channel 6. For this purpose, the spin polarization channel 6 is covered with the C12 diamond protective layer 7.

[0061] The C12 diamond protective layer 7 is grown using a CVD process in the same way as the diamond matrix 3. The spin polarization channel 6 and those areas of the diamond matrix 3 from which the diamond layer 5 has been completely removed serve as the basis for the growth of the C12 diamond protective layer 7.

[0062] A C13-free growth gas 8 is used to grow the C12 diamond protective layer 7, so that the C12 diamond protective layer 7 is nuclear spin-free after completion of the growth.

[0063] This C12 diamond protective layer 7 can protect the spin polarization channel 6 from negative external influences and contribute to increasing the coherence time of the defect centers 4. This is achieved by the C12 diamond protective layer 7 being C13-free. It therefore does not contain any diamond atoms with nuclear spins that could couple to the spins of the defect centers 4 or the spin polarization channel 6 and thus negatively affect the coherence time.

[0064] In addition, the C12 diamond protective layer 7 can serve as a protective layer to protect the spin polarization channel 6 from mechanical damage.

[0065] The C12 diamond protective layer 7 can provide a spin information transport device 1, which, compared to a spin information transport device 1 without a diamond protective layer, as described in Fig. As shown in 1e, it is even more stable and reliable.

[0066] The C12 diamond protective layer 7 has a thickness S in the range of 50 nm to 100 nm. The C12 diamond protective layer can be the same thickness as the diamond matrix 3. In this way, the spin polarization channel 6 is symmetrically enclosed and protected in the center of the layer system consisting of the C12 diamond protective layer 7 and the diamond matrix 3.

[0067] With the help of the spin information transport device 1 described above and the method for manufacturing it, it is possible to provide a device with which spin information can be transported in a directed manner. REFERENCE MARK LIST 1 Spin Information Transport Device 2 diamond substrate 3 diamond matrix 4 defect centers 5 diamond layers 6 Spin polarization channel 7 C12 diamond protective layer 8 Growth gas 9 Plasma B Width Thickness Length L M thickness S Thickness W Growth direction

Claims

Spin information transport device (1) comprising a diamond matrix (3) of C12 diamond and two defect centers (4), in particular NV centers, within the diamond matrix (3), characterized by a spin polarization channel (6) which is formed of C13 enriched diamond, to enable a directed propagation of a spin polarization which extends between the two defect centers (4). Spin information transport device (1) according to claim 1 , characterized in that the spin polarization channel (6) is arranged above the defect centers (4). Spin information transport device (1) according to one of claims 1 or 2, characterized in that the spin polarization channel (6) is covered by a C12 diamond protective layer (7). Spin information transport device (1) according to one of the preceding claims, characterized in that the diamond matrix (3) is arranged on a diamond substrate (2). Spin information transport device (1) according to one of the preceding claims, characterized in that the spin polarization channel (6) has a width (B) of 1 nm to 10 µm, a length (L) of at least 5 nm, preferably at least 500 nm, particularly preferably in the range of 500 nm to 1 µm, and / or a thickness (D) in the range of 0.5 nm to 100 nm. Spin information transport device (1) according to one of the preceding claims, characterized in that the diamond matrix (3) has a thickness (M) of at least 50 nm, in particular at least 100 nm. Method for producing a spin information transport device (1) comprising the steps: • Growing a diamond matrix (3) of C12 enriched diamond onto a, in particular ultrapure, diamond substrate (2) by means of CVD; • Introducing defect centers (4) into the diamond matrix (3); • Growing a C13 enriched diamond layer (5); • Partially removing the C13 enriched diamond layer (5), in particular by etching, to form a spin polarization channel (6). Method according to claim 7, characterized in that a C12 diamond protective layer (7) is grown on the spin polarization channel (6) to increase the coherence time of the defect centers (4). Method according to one of claims 7 or 8, characterized in that the growth of the C13 enriched diamond layer (5) is carried out by means of CVD using C13-enriched methane gas. Method according to one of claims 7 to 9, characterized in that the area-wise removal of the C13 enriched diamond layer (5) is carried out by means of controlled plasma etching, in particular ICP, of the surface of the C13 enriched diamond layer (5).

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