Magnetic component, in particular quantum component

Abstract

The invention relates to a magnetic component comprising a substrate (6) supporting at least one pair of permanent magnets (2) extending in a first direction (X), each magnet (2) having interaction ends (21a, 21b) arranged to face each other, the pair of magnets (2) is arranged to apply an antisymmetric magnetic field having a high magnetic field gradient along a second direction (Z) orthogonal to the first direction (X) under the action of a magnetic field generated by an external magnetic device.

Description

[0001] The present invention relates to magnetic components in the field of microelectronics and nanoelectronics, in particular quantum components. Quantum components are particularly, but not exclusively, used to make quantum computers. They may also be of interest in the fields of spin electronics, topological superconductivity, magnetic actuation of nanoelements and nanobeads, or near-field magnetic detection using scanning probes.

[0002] There are devices designed to generate a magnetic field in a specific direction via magnets, referred to as micromagnets by those skilled in the art in the field of microelectronics and nanoelectronics.

[0003] One object of the present invention is to propose a new quantum component architecture making it possible to significantly reduce the quantum misalignment observed in prior art quantum components and thus improve the performance of these components. Summary of the invention

[0004] To this end and according to a first aspect, the present invention provides a magnetic component, which includes a substrate supporting at least a pair of permanent magnets extending in a first direction, each magnet having an interaction end, which is arranged to face each other, and the pair of magnets are arranged to apply an antisymmetric magnetic field with a high magnetic field gradient along a second direction orthogonal to the first direction relative to the X=0 plane under the action of a magnetic field generated by an external magnetic device, and to apply a symmetric magnetic field along the first direction (X) orthogonal to the Y direction and the Z direction relative to the X=0 plane.

[0005] For the foregoing and for the remainder of the specification, the following terms have the following definitions:

[0006] - Quantum components, components of electronic circuits and / or devices using nanotubes as their conducting or semiconducting elements, the circuits having single, two or more quantum dots connected in series or in parallel, using a single nano-object with selected properties as a channel element, or using a plurality of individually selected nano-objects;

[0007] - Quantum dot, a part of a nano-object in which an electron is trapped / confined in three dimensions; it can occupy only discrete energy levels;

[0008] - nano-object, an object whose external dimensions (usually from its height, width, thickness, length) are less than 100 nanometers; if its three external dimensions (defined along three orthogonal axes) are less than 100 nanometers, it is a nanoparticle; if two of its external dimensions (preferably defined along two orthogonal axes) are less than 100 nanometers, it is, for example, a hollow single-walled or multi-walled nanotube that may be closed at least at one end or a nanofiber, which is a solid fiber. Conductive or semiconducting nanofibers will subsequently be referred to as nanowires. If the external dimensions are less than 100 nm (usually their thickness), they are nanosheets;

[0009] - electrodes, ends of electrical conductors arranged to release or capture electric current;

[0010] - a gate electrode, an electrode that transmits the microwave signal or makes it possible to set the potential (in volts);

[0011] - A microwave gate electrode, a gate electrode that transmits and radiates a microwave signal that allows interaction between the microwave cavity and the nano-object;

[0012] - a low frequency gate electrode that allows the electrostatic potential to be set and creates a double quantum dot;

[0013] - magnet, a magnetic element that is magnetized under the influence of an external magnetic field;

[0014] - an electrostatic potential capable of forming two quantum dots, which allows the potential energy barrier to be adjusted and a double quantum dot to be generated;

[0015] - Spin-photon coupling, the controllable interaction or "coupling" between the magnetic appearance of the qubit (i.e. its spin) and the microwave electric field from the microwave cavity. Since the electric field is composed of photons, we call it spin-photon coupling;

[0016] - Quantum gates, logical operations that can change the superposition state of a qubit. For example, a qubit can be in one of two states with a 50% probability and in the other of two states with a 50% probability;

[0017] a non-uniform magnetic field, preferably a magnetic field generated by any variation of the magnetic field around and / or along at least one nano-object element so as to generate a magnetic dipole; for example, a vertical and / or horizontal component of the magnetic field changes its sign along or around at least one nano-object element, preferably at or perpendicular to at least one magnetic grid electrode; according to a specific example, a magnetic field gradient horizontally or along the at least one nano-object element makes the total magnetic field non-uniform along the at least one nano-object element, preferably, a magnetic field component along an axis or direction of the at least one nano-object changes its sign along the at least one nano-object element;

[0018] - a spatial extent, according to one embodiment, preferably radially along and / or around a region where the at least one nano-object element is located, preferably between the suspended electrodes, corresponding to the extent of the distance between two quantum dots;

[0019] - Substrates, in particular elements of components having a high resistivity (eg a higher dielectric constant than air) at low temperatures.

[0020] According to a second aspect of the present invention, a quantum component is provided, the quantum component comprising:

[0021] at least two suspended electrodes: a source electrode connected to an electron source and a drain electrode connected to a reference potential, the source electrode and the drain electrode being designed to receive a quantum element integrated with double quantum dots,

[0022] at least three gate electrodes are arranged between the two suspension electrodes, the two suspension electrodes are raised relative to the at least three gate electrodes,

[0023] According to the magnetic component of the present invention, the magnetic component is designed to apply an antisymmetric magnetic field having a high magnetic field gradient along a second direction orthogonal to the first direction under the effect of a magnetic field generated by an external magnetic device, and the antisymmetric magnetic field is applied to the quantum element.

[0024] According to a third aspect of the present invention, a method for manufacturing a quantum component according to the present invention is provided, the method comprising the following steps:

[0025] - etching the substrate to receive the magnetic elements,

[0026] - depositing at least one pair of magnets extending in a first direction (X), each magnet having an interaction end arranged facing each other,

[0027] - performing a low angle etch on the substrate on which at least one pair of magnets is deposited,

[0028] - depositing an oxide layer on the treated substrate,

[0029] - Depositing the floating electrode and the gate electrode on the oxide layer.

[0030] Preferably, according to any of the aforementioned aspects, the component or method may include one or more of the following features:

[0031] - the magnet pair itself produces an antisymmetric magnetic field (z-axis component) between the two points (relative to the x=0 plane), and the applied external magnetic field produces a symmetric field between the two points;

[0032] - between quantum dots separated by distances between 60 and 120 nanometers, these gradients result in asymmetric field components that can reach approximately 30 mT or 40 mT (millitesla);

[0033] -If we consider points placed symmetrically with respect to the field distribution, the field in the two points of the double quantum dot will consist of a symmetric part and an antisymmetric part.

[0034] For each field component it is possible to define: i = u,v,w:

[0035]

[0036] Where L, R refers to the left (L) and right (R) quantum dots, respectively. This definition of the symmetric / asymmetric magnetic field for each vector component i (where u, v, w refer equivalently to directions in space x, y, z). This definition makes sense in the context of double quantum dots.

[0037] The effect of the stray field on the energy in the left and right parts of the double quantum dot can then be expressed as:

[0038]

[0039] in

[0040] |ψ p (r)| 2

[0041] is the probability density of the existence of an electron in point p (left or right), the prefactor 2 represents the Landé factor of the electron spin, and μB is the Bohr magneton.

[0042] This corresponds to the mathematical definition of the magnetic coupling constant between the electrons in the quantum dot and the symmetric or antisymmetric magnetic field. We will see later which is considered to be the quantity to be optimized (maximized).

[0043] Therefore, the gradient must be considered as the inhomogeneity between two quantum points of the field averaged over each point.

[0044] Now consider a pair of dots with linear confinement, as found in double quantum dots in nanowires. These dots are arranged along x and are confined between -250nm and -150nm for dot L and 150nm for dot R. nm Up to 250 nm between.

[0045] Nanowires with z = 200 nm Suspended

[0046] Over a magnetic layer extending in -100 nm < z < 100 nm.

[0047] Since the external magnetic field is preferably applied along the nanowire, whereas a transverse gradient is required, we assume a uniform magnetization along +x.

[0048] Since we are now considering points that are above the magnetic system, we use:

[0049] Q = ∫B y / z (x)|ψ L (x)| 2 dx-∫B y / z (x)|ψ R (x)| 2 dx

[0050] where L and R are exchanged with respect to the above. The definition of Q is the quantity being optimized (see previous coupling constants between magnetic field and point).

[0051] To ensure the actual shape, constraints are added so that the magnet is uniform along z.

[0052] The optimization therefore consists in deciding whether there is a magnet in each or one or more cells or one or more elements of the total thickness along the Z axis at all X and Y positions. This method of optimizing this quantity Q is linear with respect to a single magnetic element / cell;

[0053] A higher magnetic saturation MS directly favors higher parasitic fields and gradients; it also promotes the formation of magnetic domains in the nanomagnet and thus requires a higher external field to reach saturation.

[0054] The external field

[0055] α ext =2μ B B ext

[0056] In the symmetric part of the parasitic field from the point level formation a s is added as an item.

[0057] By defining the inhomogeneity of the field acting on a point as

[0058] α as / (α s +α ext ),

[0059] When strong external fields are used, this quality factor decreases.

[0060] In order to optimize the inhomogeneity, it is therefore necessary to identify the pair of MS and Bext values ​​that provides the highest value of:

[0061] α as / (α s +α ext )

[0062] This last point corresponds to the definition of the contribution of the external magnetic field to this symmetric component. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Other features and advantages of the present invention will become apparent from the following detailed description of the invention made with reference to the accompanying drawings, and in which:

[0064] [ Figure 1 ][ Figure 1 ] is a schematic diagram of a quantum component including electrodes extending substantially perpendicular to two series of magnets according to one embodiment;

[0065] [ Figure 2 ][ Figure 2 ] shows two series of magnets extending parallel to each other within the same series and between the two series, wherein the ends of the magnets of the first series face the ends of the magnets of the second series and the magnets of the two series lie in the same plane;

[0066] [ Figure 3 ][ Figure 3 ] is a schematic diagram of two magnet ends facing each other and a nanotube connecting the two ends according to an embodiment of a quantum component, the schematic diagram being arranged in a three-dimensional reference system;

[0067] [ Figure 4 ][ Figure 4 ] is a nanoscale depiction of the saturation of the magnetic field at the ends of the two magnets;

[0068] [ Figure 5 ][ Figure 5 ] shows the curves of the magnetic field components along the carbon nanotube, especially using the [ Figure 2 ] magnetic field distribution along carbon nanotubes obtained by micromagnets;

[0069] [ Figure 6 ][ Figure 6 ] shows the influence of an external magnetic field on various physical quantities with three different magnet materials.

[0070] For greater clarity, the same or similar elements in the various embodiments are denoted by the same reference numerals in all drawings. DETAILED DESCRIPTION

[0071] about Figure 1 and Figure 2 , shows an embodiment of a quantum component 1, the embodiment comprising:

[0072] A substrate 6, which is made of a high resistivity material, for example,

[0073] a magnetic device 2, serving as a magnetic electrode, arranged to generate a magnetic field to which the quantum component 1 is subjected, comprising two comb-shaped portions 2A, 2B arranged facing each other and separated by a central gap 22 in which a dedicated magnetic field is generated,

[0074] A set of gate electrodes 8 are placed above the central gap 22, which are surrounded by a source electrode 9.1, a cut source electrode 9.2, a cut drain electrode 9.3 and a drain electrode 9.4,

[0075] Nanotubes or nanowires connected to suspended electrodes (in [ Figure 1 ]), the nanotube or nanowire is suspended linearly above a gate electrode and above a set of substantially parallel magnets, preferably made of carbon.

[0076] The source and drain electrodes are placed on the conductive layer via an insulating layer. They act as suspended electrodes for the nanotubes or nanowires and protrude above the gate electrode. This arrangement is specific to quantum components that include carbon nanotubes.

[0077] Reference [ Figure 2 ], the magnetic device 8 comprises permanent magnets arranged in the form of two opposing combs 2A, 2B (a first comb and a second comb). Each comb 2A, 2B comprises a plurality of generally rectangular magnets 20A, 21A; 21A, 21B arranged parallel to each other. A series of magnets in each comb is connected to two opposite ends of the pair along the Z axis.

[0078] According to the embodiment shown, each comb 2A, 2B comprises 15 magnets. Each magnet is 1.5 microns wide and 8.5 microns long. The width is selected so that the magnetic moment is parallel to the boundary due to the internal dipole energy. Preferably, each magnet is spaced apart by a distance of 0.75 microns laterally along the Y axis. Preferably, each comb 2A, 2B has a thickness of 400 nanometers. Preferably, each magnet comprises iron and cobalt, preferably with high remanence.

[0079] Reference Figure 2 and Figure 3 , each magnet 21A of the first comb 2A has an interaction end or pole 41A arranged to face the interaction end or pole 41B of the magnet 21B of the second comb 2B. Each transverse face is opposite to a transverse face of a magnet on the second comb. Preferably, the distance between the two interaction ends or poles is between 0.4 micrometers and 1 micrometer. The spacing is measured between the distal points of the interaction ends.

[0080] Preferably, when following the Figure 2 ], each interaction end has a rounded shape when viewed in a two-dimensional plane or a longitudinal plane as shown in the XY plane in FIG. Figure 3 , Figure 4 and Figure 5 The optimal shape of the saturated nanomagnet in the case of a quantum dot of finite extension is shown, in particular for a uniform magnetization applied along x, thereby maximizing the field difference Bz. Preferably, a rounded distal end portion, in particular a three-dimensional ovoid, is most conducive to magnetic field optimization. The shape of the interacting end aligns the magnetic moment in a single direction.

[0081] In addition, each magnet 21A has a connection end 31A opposite to the interaction end 41A. Each comb 2A, 2B also comprises a magnet connection piece 200A, 200B, so that each magnet of the comb 2A, 2B is connected to the connection piece 200A, 200B of the comb 2A, 2B via a connection end. According to the embodiment shown, the connection piece 200A, 200B is 4 microns wide.

[0082] This embodiment provides anisotropic shape and produces a uniform magnetic field in the Y direction of the nanotube.The reduced size of the magnet results in shape anisotropy, with the magnetic moments tending to be parallel to the boundaries due to the internal dipole energy.

[0083] Preferably, the two magnet combs 2A, 2B are embedded in the base plate 6 .

[0084] In addition, the quantum component comprises external magnetic means (not shown) arranged to apply a magnetic field in the X direction. For example, a toroidal coil (not shown) surrounds the electrodes and the comb. Preferably, the toroidal coil generates a magnetic field between 200 millitesla and 500 millitesla.

[0085] Therefore, the quantum component proposes to apply an antisymmetric magnetic field with a strong magnetic field gradient along the Z direction orthogonal to the X direction under the action of a magnetic field generated by an external magnetic device. For example, according to the tests conducted, the antisymmetric field constant reached 26.8 micro-eV and the symmetric field constant reached 29 micro-eV, making it possible to optimize the spin-photon coupling.

[0086] The quantum component optimizes the magnetic moment distribution around the quantum dots, the magnetic field gradient and therefore the interaction between the magnet and the nano-object or nano-tube comprising at least two quantum dots. Preferably, the nano-object or nano-tube is about 100 nanometers above the magnet pair under consideration.

[0087] [ Figure 6 ] show the results of micromagnetic simulations for a shape optimized for an inhomogeneous component Bz with an external field Bext and the magnetization along x. Based on the external magnetic field, (a) the magnetization mx, (b) the symmetry (αs), (c) the antisymmetric (αas) coupling constant due to the nanomagnet, and (d) the ratio between the antisymmetric field and the total symmetric field.

[0088] α as / (α s +α ext )

[0089] The different colors correspond to CoFe (line with squares), Co (line with triangles), and NiFe (line with circles).

Claims

1. A magnetic component, comprising a substrate (6), the substrate receiving at least one pair of permanent magnets extending in a first direction (X), each magnet having an interaction end, the interaction ends being arranged to face each other, the pair of magnets being arranged to apply an antisymmetric magnetic field having a high magnetic field gradient along a second direction (Z) orthogonal to the first direction (X) relative to an X=0 plane under the action of a magnetic field generated by an external magnetic device, and to apply a symmetric magnetic field along the first direction (X) orthogonal to a Y direction and a Z direction relative to the X=0 plane.

2. The magnetic component according to claim 1, comprising several pairs of magnets facing each other so as to form two combs.

3. The magnetic component according to claim 1 or 2, wherein: Each magnet has a linear shape.

4. The magnetic component according to any one of claims 1 to 3, wherein: The interacting end of each magnet has a rounded shape.

5. The magnetic component according to claim 4, characterized in that: The rounded shape is a curve having a predetermined radius of curvature.

6. The magnetic component according to claim 4 or 5, wherein: Each magnet end is three-dimensionally rounded.

7. The magnetic component according to any one of claims 1 to 6, wherein: The interacting end of each magnet has a shape without protrusions.

8. The magnetic component according to any one of claims 1 to 7, wherein: The at least one magnet is embedded in the substrate.

9. The magnetic component according to any one of claims 1 to 7, wherein: The at least one magnet is deposited on the substrate.

10. A quantum component, comprising: - a source electrode connected to an electron source and a drain electrode connected to a reference potential, said source electrode and said drain electrode being designed to receive a quantum element in which a double quantum dot is integrated, - at least three gate electrodes (9.1, 9.2, 9.3, 9.4) arranged between the source electrode and the drain electrode, - A magnetic component (1) according to any one of claims 1 to 9, wherein the magnetic component is designed to apply an antisymmetric magnetic field having a high magnetic field gradient along a second direction (Z) orthogonal to the first direction (X) under the action of a magnetic field generated by an external magnetic device, and the antisymmetric magnetic field is applied to the quantum element.

11. The quantum component according to claim 10, characterized in that The source electrode and the drain electrode constitute floating electrodes protruding relative to the at least three gate electrodes.

12. The quantum component according to claim 11, further comprising at least a nano-object element (11) as a quantum element, wherein the nano-object element is suspended between the two suspended electrodes and electrically connected to the two suspended electrodes, and the at least one nano-object element is arranged above the at least three gate electrodes. 13 . The quantum component according to claim 10 , further comprising an electron gas as a quantum element, the electron gas being located in a substrate disposed between the source electrode and the drain electrode.

14. The quantum component according to one of claims 10 to 13, wherein The quantum element is arranged at a distance of approximately 100 nm above the at least one magnet pair.

15. The quantum component according to one of claims 10 to 14, wherein The pair of magnets are arranged symmetrically with respect to a plane orthogonal to the direction of the at least one quantum element.

16. A method for manufacturing a quantum component according to one of claims 10 to 15, the method comprising the following steps: - etching the substrate to receive the magnetic elements, - depositing at least one pair of magnets extending in a first direction (X), each magnet having an interacting end arranged facing each other, - performing a low angle etch on said substrate on which at least one pair of magnets is deposited, - depositing an oxide layer on the treated substrate, - Depositing a floating electrode and a gate electrode on the oxide layer.

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