Quantum computing arrangement and quantum computer

Abstract

A quantum computing arrangement (1) is specified, comprising a permanent magnet arrangement (2) having a plurality of permanent magnetization segments (3). The quantum computing arrangement is configured to implement a Porro trap (100) for trapping ions along a predefined line (7). Each segment has a magnetization direction (4). The segments are arranged such that the magnetization directions of at least some segments differ from each other and such that a magnetic field is established, the size of which varies along a predefined line. Furthermore, a quantum computer (8) comprising the quantum computing arrangement (1) is specified.

Description

[0001] The present disclosure relates to quantum computing arrangements and quantum computers.

[0002] In many quantum computing processes using quantum computing arrangements, the arrangements are configured to trap quantum particles such as ions. During operation, the trapped quantum particles form quantum bits, or qubits for short. In order to perform calculations, the trapped quantum particles must be controlled and manipulated. For trapped quantum particles, interactions such as Coulomb repulsion can produce coupling of adjacent trapped quantum particles and thereby achieve entanglement. In order to perform quantum computing processes using trapped quantum particles, the trapped quantum particles must be controllable and individually addressable from each other.

[0003] Individual addressing of multiple trapped quantum particles (e.g., qubit registers) is desirable with negligible crosstalk. However, crosstalk between adjacent trapped quantum particles is often a difficult-to-control error source in quantum computer processing and may prevent meaningful application of quantum error correction protocols and, thus, scalability.

[0004] Therefore, one object to be achieved is to provide an improved quantum computing arrangement, for example a quantum computing arrangement allowing improved controllability. A further object to be achieved is to provide a quantum computer having such a quantum computing arrangement.

[0005] These objects are solved in particular by the subject matter of claim 1 and claim 16. Advantageous embodiments and further developments are the subject matter of the dependent claims and can also be taken from the following description and the drawings.

[0006] First, the quantum computing arrangement is described in detail.

[0007] According to at least one embodiment, a quantum computing arrangement includes a permanent magnet arrangement. The permanent magnet arrangement includes a plurality of permanently magnetized segments.

[0008] The segments can be formed all identically within the limits of manufacturing tolerances. For example, the permanent magnet arrangement is symmetrical, in particular geometrically symmetrical, with respect to the symmetry plane. This means that the geometry or shape of the permanent magnet arrangement is symmetrical with respect to the symmetry plane, respectively. The geometry of the permanent magnet arrangement can also have rotational symmetry, for example n-fold rotational symmetry, where n is at least 3 or at least 4 or at least 6 or at least 8.

[0009] The permanent magnet arrangement may comprise at least four or at least eight or at least 16 or at least 32 segments. Each segment comprises or consists of a permanent magnetic material. For example, the permanent magnetic material is a ferromagnetic material. The segments may each comprise or consist of the same material. Each segment is, for example, integrally formed. Alternatively, each segment is formed of at least two sub-segments, wherein at least two sub-segments have the same material and / or magnetization properties.

[0010] According to at least one embodiment, the quantum computing arrangement is configured to implement a Paul trap for trapping ions along a predefined line (i.e., the ions are arranged along a predefined line). In other words, during operation, the quantum computing arrangement (i.e., at least a portion thereof) constitutes a Paul trap. A Paul trap is also known as a quadrupole ion trap or a radio frequency (RF) trap. A Paul trap is an ion trap that uses a dynamic electric field to trap charged particles.

[0011] The Paul trap comprises a plurality of electrodes, for example at least two RF electrodes, at least two DC electrodes and at least two end cap electrodes. The electrodes may be different from the permanent magnetized segments of the permanent magnet arrangement. Thus, the Paul trap may be an independent device in the quantum computing arrangement that is different from the permanent magnet arrangement. Alternatively, one or more of the segments of the permanent magnet arrangement also form electrodes of the Paul trap, so that the Paul trap is at least partially formed by the permanent magnet arrangement.

[0012] The Paul trap is configured to trap 2 or more (eg, at least 8 or at least 20 or at least 100 and / or at most 1000) ions along a predefined line.

[0013] During operation, the electrodes of the Paul trap generate an oscillating potential configured to trap ions in a direction parallel to the predefined line and in a direction perpendicular to the predefined line (also referred to herein as a radial direction). Effectively, at least one potential well is generated in which ions are trapped in all specific directions and the potential well is formed so that the ions are arranged one after another along the predefined line. Multiple ions trapped in the same electrostatic potential well are also referred to herein as an ion crystal.

[0014] The predefined line (also referred to as the trapping line) is defined by the potential generated by the Paul trap and therefore depends on the geometry of the Paul trap. The trapped ions are arranged along the predefined line. For example, each of the ions intersects the predefined line and / or oscillates around the predefined line. In other words, in the Paul trap, the ions are arranged in an ion chain extending along the predefined line.

[0015] In addition to electrodes for the Paul trap, the quantum computing arrangement may also comprise components for powering the electrodes, such as a power supply and / or a control unit.

[0016] According to at least one embodiment, each segment has a magnetization direction. The magnetization of each segment is defined by a vector field representing the dipole moment of the corresponding permanent magnetic material. That is, the corresponding permanent magnetic material exhibits a dipole moment. The vector field (in particular the dipole moment of the permanent magnetic material) defines the corresponding magnetization direction. The dipole moment points substantially in the magnetization direction.

[0017] According to at least one embodiment, the segments are arranged such that the magnetization directions of at least some of the segments differ from each other, such that the permanent magnet arrangement establishes a magnetic field.The magnitude of the magnetic field varies along a predefined line.

[0018] For example, the magnetization directions of every two directly adjacent segments are different from each other. The magnetization directions may differ from each other by an angle of at least 5° or at least 10° and / or at most 90° or at most 45°. For example, if there are m segments, where m is an even natural number of at least 4, the magnetization directions of every two directly adjacent segments are rotated relative to each other by 360°·3 / m.

[0019] The vector field defined by the magnetization directions of the segments and the positions of the segments in space may be symmetrical with respect to the above-mentioned symmetry plane. In particular, the vector field may have the same symmetry as the geometry of the permanent magnet arrangement. Alternatively, the vector field may be asymmetrical with respect to the symmetry plane and / or may have a different symmetry than the geometry of the permanent magnet arrangement or may even be asymmetrical.

[0020] The magnetic field is understood in this article as the magnetic flux density. Therefore, the magnitude of the magnetic field is the absolute value of the magnetic flux density.

[0021] The magnetic field generated by the permanent magnet arrangement is, for example, a magnetic quadrupole field or includes, for example, a magnetic quadrupole field. Higher multipole moments may also exist. At the center of the magnetic field, the absolute value of the magnetic field may be zero. The center of the magnetic field may coincide with the geometric center of the permanent magnet arrangement and / or the geometric center of the Paul trap. For example, the center of the magnetic field is located in the symmetry plane of the permanent magnet arrangement and / or on a predefined line. The magnetic field may be point-symmetric relative to its center.

[0022] The magnitude of the magnetic field changes along the predefined line. This means that the magnitudes of the magnetic field at different locations on the predefined line are different from each other. The change in the magnitude of the magnetic field along the predefined line is also referred to herein as the gradient of the magnetic field along the predefined line.

[0023] The change in the magnitude of the magnetic field may be monotonic, e.g. strictly monotonic, at least in part. For example, starting from the center of the magnetic field, the change in the magnetic field may be monotonic or strictly monotonic in two directions along a predefined line. The direction of the magnetic field may change along the predefined line or may remain constant along the predefined line.

[0024] In at least one embodiment, a quantum computing arrangement includes a permanent magnet arrangement having a plurality of permanently magnetized segments. The quantum computing arrangement is configured to implement a Paul trap for trapping ions along a predefined line. Each segment has a magnetization direction. The segments are arranged so that the magnetization directions of at least some of the segments are different from each other and so that a magnetic field is established whose magnitude varies along the predefined line.

[0025] Trapped ions provide excellent quantum systems for quantum control and metrology. In the present invention, the trapped ions are stored in a Paul trap and form at least one ion crystal oriented along a predefined line. For quantum computing with trapped ions and for certain tasks in metrology, it is desirable to individually control individual ions. When ions are manipulated by RF radiation, such single ion control cannot be achieved by focused radiation because the wavelength typically exceeds the ion spacing in the ion crystal by several orders of magnitude. In addition, the coupling of internal quantum states quantified by Lamb-Dicke parameters to external quantum states cannot be achieved by RF radiation.

[0026] The invention is based inter alia on the idea of ​​using an inhomogeneous magnetic field provided by a permanent magnet arrangement to resolve the resonant degeneracy of the individual trapped ions. This provides the possibility of individually addressing the ions in frequency space by means of RF radiation. On the other hand, the superposition of the potential caused by the Paul trap and the magnetic field of the permanent magnet arrangement makes the equilibrium position of the ions depend on their respective quantum states. Thus, an effective spin-spin coupling is achieved by the Coulomb interaction between the trapped ions. This enables the quantum states of the ions to be entangled.

[0027] In summary, using the described quantum computing arrangement for quantum information processing, high-level addressing can be achieved in frequency space, and thus individual single qubit rotations with low crosstalk are achieved, and effective coupling between ions is introduced, thereby achieving multi-qubit gates. The quantum computing arrangement can also be used in combination with RF frequencies. For RF frequencies, addressing by focused radiation is not possible due to the longer wavelength, but RF fields can provide advantages in miniaturization and integration. According to at least one embodiment, the permanent magnet arrangement includes NdFeB. In particular, the permanent magnet arrangement includes NdFeB N52. Exemplarily, each segment includes NdFeB or consists of NdFeB, and in particular includes NdFeB N52 or consists of NdFeB N52.

[0028] According to at least one embodiment, the segments are arranged in a Halbach arrangement. The Halbach arrangement is a special arrangement of permanent magnets that enhances the magnetic field on one side thereof and cancels the field to near zero on the other side. In particular, this is achieved by having a spatially rotating pattern of the magnetization direction of the segments.

[0029] With such a Halbach arrangement, particularly high magnetic fields and magnetic field gradients can be achieved. Since the effective spin-spin coupling and the difference in the resonance of neighboring ions depend on the inhomogeneity and size of the magnetic field, the Halbach arrangement is particularly useful. In fact, even when the distance between any surface (including the surface of the trapping electrodes and the magnet) and the trapped ions should be large, the Halbach arrangement allows large gradients, which is desirable for high-fidelity gates with trapped ions.

[0030] According to at least one embodiment, the permanent magnet arrangement surrounds the Paul trap. That is, the Paul trap is a device independent of the permanent magnet arrangement. In particular, the segments of the permanent magnet arrangement are different from the electrodes of the Paul trap. For example, the permanent magnet arrangement has the shape of a ring, or has a polygonal outline or peripheral shape, respectively. Therefore, the Paul trap can be surrounded by a permanent magnet arrangement in the shape of a ring or a permanent magnet arrangement in the shape of a polygonal outline. The permanent magnet arrangement can then enhance the magnetic field in the interior of the ring or outline, and offset the magnetic field to near zero outside the other side of the ring or outline.

[0031] According to at least one embodiment, at least some electrodes of the Paul trap are formed by segments of a permanent magnet arrangement. For example, the end cap electrodes are formed by segments of a permanent magnet arrangement.

[0032] According to at least one embodiment, the Paul trap is a linear Paul trap for trapping ions along a predefined straight line or axis, respectively. Hence, the predefined line is a predefined straight line or a predefined axis, respectively. Alternatively, the Paul trap may be a circular Paul trap.

[0033] According to at least one embodiment, the quantum computing arrangement further comprises a yoke structure for increasing the change in the magnetic field and / or the magnitude of the magnetic field along the predefined line established by the permanent magnet arrangement. The yoke structure is particularly arranged so that it increases the magnetic field or magnetic field gradient in the region of the trapped ions (i.e., along the predefined line). For example, the yoke structure comprises or is composed of a soft magnetic material. The yoke structure may have a coercive force of at most 1000 A / m or at most 100 A / m. The soft magnetic material may be a ferromagnetic material configured to be magnetized by a magnetic field established by the permanent magnet arrangement. The soft magnetic material may have a relative magnetic permeability of at least 300 or at least 1000 or at least 10000. Exemplarily, the soft magnetic material has a relative magnetic permeability of about 12000. The saturation magnetic flux density of the soft magnetic material may be at least 0.5 T or at least 2 T. For example, the soft magnetic material comprises at least one of the following: iron, cobalt, vanadium, manganese, niobium, silicon, carbon.

[0034] The yoke structure may extend along the predefined line or parallel to the predefined line. For example, the yoke structure comprises at least two parts spaced apart from each other in a direction parallel to the predefined line. Each of the two parts may be elongated, for example having a main extension direction parallel to or along the predefined line. That is, the elongated part may be oriented parallel to the predefined line. Parts of the yoke structure may intersect the predefined line.

[0035] The steepness of the magnetic gradient can be further enhanced by using a yoke structure to concentrate the magnetic flux. The yoke structure is for example placed in a region of the permanent magnet arrangement where the magnetic field already has a small magnitude and concentrates it to a small cross section of the yoke structure without exceeding the saturation magnetization of the yoke structure, thereby significantly increasing the magnitude of the achievable gradient, allowing lower crosstalk, stronger coupling and faster quantum gates.

[0036] According to at least one embodiment, the yoke structure is at least partially formed by components of end cap electrodes of a quantum computing arrangement constituting a Paul trap (hereinafter referred to as end cap electrodes of the Paul trap). The end cap electrodes (irrespective of whether they are part of the yoke structure) are, for example, formed as elongated elements extending parallel to a predefined line or along a predefined line. The end cap electrodes may each include a cylindrical body. In addition, each end cap electrode may include a tapered portion, such as a conical portion. The tapered portions taper toward each other or toward the trapped ions, respectively.

[0037] For example, each of the end cap electrodes forms part of the yoke structure.The end cap electrodes may intersect the predefined line.

[0038] Further electrodes of the Paul trap may also be part of the yoke structure.In other words, at least some electrodes of the Paul trap may comprise or consist of a soft magnetic material in order to increase the magnetic field or magnetic field gradient established by the permanent magnet arrangement.

[0039] According to at least one embodiment, the yoke structure is arranged between the end cap electrodes of the Paul trap. For example, parts of the yoke structure are arranged between the end cap electrodes in a direction parallel to the predefined line.

[0040] According to at least one embodiment, the yoke structure comprises or consists of an iron-cobalt alloy.The iron-cobalt alloy may comprise vanadium, for example with a concentration of at least 1.5% and at most 3%.

[0041] According to at least one embodiment, the quantum computing arrangement includes a vacuum chamber. During operation, ions are trapped in the vacuum chamber. The Paul trap or its electrodes may also be arranged in the vacuum chamber. The vacuum chamber may be an ultra-high vacuum chamber, an extremely high vacuum chamber and / or a cryostat.

[0042] According to at least one embodiment, the permanent magnet arrangement is arranged outside the vacuum chamber. This can be advantageous because the creation of an ultra-high vacuum (UHV for short) can involve steps such as baking, which may be incompatible with many magnetic materials, particularly magnetic materials with a low Curie temperature. Even when located outside the vacuum chamber, the permanent magnet arrangement still generates a sufficiently high magnetic field or magnetic field gradient in the ion region. Alternatively, the permanent magnet arrangement can also be located inside the vacuum chamber. An optional yoke structure can be arranged inside or outside the vacuum chamber and can increase the magnetic field (gradient).

[0043] According to at least one embodiment, the permanent magnet arrangement establishes a substantially two-dimensional magnetic field, which is mainly concentrated in the magnetic field plane. The center of the magnetic field can be located in the magnetic field plane. The symmetry plane of the permanent magnet arrangement is, for example, perpendicular to the magnetic field plane. For example, all of the segments of the permanent magnet arrangement are arranged in the magnetic field plane.

[0044] When starting from the magnetic field plane and moving in a direction perpendicular to the magnetic field plane, the magnetic field decays, for example the average magnitude of the magnetic field decays to almost zero. The decay length depends on the size of the permanent magnet arrangement, for example on the inner radius and / or outer radius and / or thickness of the segment measured perpendicular to the magnetic field plane. In particular, the decay length is proportional to the inner radius and / or outer radius and thickness of the segment.

[0045] For example, the average magnitude of the magnetic field has a full width at half maximum (FWHM) of at least 1 μm or at least 10 μm and / or at most 10 mm or at most 500 μm in a direction perpendicular to the magnetic field plane. For example, in this case, the average magnitude of the magnetic field outside the magnetic field plane (e.g. at a distance of 1 mm from the magnetic field plane) is at least one order of magnitude smaller than the average magnitude of the magnetic field in the magnetic field plane. In other words, the magnetic field plane is the main extension plane of the magnetic field magnitude.

[0046] For example, in the case of a permanent magnet arrangement in which the segments are arranged in the form of a ring, wherein the main extension plane of the ring defines the xy plane, the magnetic flux density corresponding to the magnetic field for:

[0047]

[0048] B R is the remanence of the segment, R i is the inner radius of the ring, R o is the outer radius of the ring, and x and y are the coordinates within the permanent magnet arrangement. In this case, the magnetic field plane is the xy plane or the main extension plane of the ring, respectively.

[0049] According to at least one embodiment, the predefined line extends parallel to the plane of the magnetic field. For example, the predefined line extends in the plane of the magnetic field.

[0050] According to at least one embodiment, components of the quantum computing arrangement constituting the RF electrodes of the Paul trap (hereinafter referred to as the RF electrodes of the Paul trap) are arranged outside the magnetic field plane. For example, the two RF electrodes of the Paul trap are arranged on different sides of the magnetic field plane. Similarly, the DC electrodes of the Paul trap can be arranged outside the magnetic field plane and can, for example, be arranged on different sides of the magnetic field plane.

[0051] According to at least one embodiment, the end cap electrodes of the Paul trap are arranged in the magnetic field plane, i.e. intersecting the magnetic field plane. For example, the end cap electrodes are arranged on a predefined line, i.e. intersecting the predefined line. Alternatively, the end cap electrodes can each be split into at least two sub-electrodes, wherein the two sub-electrodes of each end cap electrode are arranged on different sides of the magnetic field plane, for example symmetrically relative to the magnetic field plane.

[0052] For example, the Paul trap comprises at least two end cap electrodes and at least four radial electrodes. The end cap electrodes may be arranged on a predefined line and spaced apart from each other in a direction parallel to the predefined line. The radial electrodes may be arranged around the predefined line. The radial electrodes may be blade electrodes. Two of the radial electrodes may be RF electrodes, which are supplied with an alternating voltage during operation. The other two of the radial electrodes may be DC electrodes, which are at a static potential (e.g., grounded) during operation. The RF electrodes are, for example, diagonally opposite to each other.

[0053] Instead of a Paul trap where electrodes are arranged on opposite sides of a magnetic field plane generated by a permanent magnet arrangement, the Paul trap may be a so called planar Paul trap where all electrodes are arranged in a common electrode plane and eg on one side of the magnetic field plane.

[0054] According to at least one embodiment, the segments of the permanent magnet arrangement are arranged in a magnetic field plane. This means, for example, that each of the segments intersects the magnetic field plane.

[0055] According to at least one embodiment, the Paul trap is configured to capture 171 Yb + ion.

[0056] According to at least one embodiment, the Paul trap is configured so that during operation, the minimum distance of directly adjacent trapped ions is at least 0.1 μm or at least 1 μm and / or at most 30 μm or at most 20 μm. The minimum distance of directly adjacent trapped ions is, for example, 5 μm. The distance of directly adjacent trapped ions can change along a predefined line. For example, two different adjacent ion crystals can have a larger distance, for example at least 50 μm or at least 100 μm. The distance between the ions can be set by setting the potential of the electrodes of the Paul trap.

[0057] According to at least one embodiment, the trapped ions each have a ± Transition, at this σ ± The magnetic quantum number changes during the transition, where the σ between directly adjacent trapped ions ± The frequency difference of the transitions is at least 50 kHz or at least 100 kHz or at least 1 MHz and / or at most 100 MHz. ± The frequency difference of the transitions is, for example, between 15 MHz and 50 MHz. ± The transition can be excited by left-circularly polarized electromagnetic waves or right-circularly polarized electromagnetic waves.

[0058] According to at least one embodiment, the trapped ions each have a π transition in which the magnetic quantum number does not change, wherein the frequency difference of the π transitions between directly adjacent trapped ions is at least 200 Hz or at least 1 kHz and / or at most 10 MHz. The frequency difference of the π transitions between directly adjacent trapped ions is, for example, between 0.001 MHz and 0.5 MHz. Such π transitions are excited by linearly polarized electromagnetic waves having a polarization parallel to the local magnetic field.

[0059] According to at least one embodiment, the edges of the segments of the permanent magnet arrangement that are arranged at the opposite area and facing each other have a minimum distance of at least 10 μm or at least 0.01 cm and / or at most 100 cm from each other. In this context, relative means, for example, relative to the center of gravity of the permanent magnet arrangement and / or relative to the center of the magnetic field.

[0060] According to at least one embodiment, each segment has an extension along a respective minimum distance of at least 10 μm or at least 0.01 cm and / or at most 100 cm. For example, each segment is formed as an annular segment. The extension along the minimum distance is then the radial extension of the segment.

[0061] According to at least one embodiment, the remanence of each of the segments of the permanent magnet arrangement is at least 0.5T and / or at most 5T.

[0062] According to at least one embodiment, the variation of the magnetic field along a predefined line (e.g. in the center of the magnetic field) is at least 0.5 T / m or at least 50 T / m or at least 100 T / m and / or at most 500 T / m. This can be achieved, for example, by the minimum distance between the relative segments and the remanence of the segments as specified above.

[0063] Next, a quantum computer is described in detail. The quantum computer includes a quantum computing arrangement as described herein. Therefore, all features disclosed for the quantum computing arrangement are also disclosed for the quantum computer, and vice versa.

[0064] The quantum computer is configured to perform a quantum computing process by using a quantum computing arrangement. Trapped ions of the quantum computing arrangement can be particularly well controlled and manipulated using the permanent magnet arrangement described herein in order to perform a predetermined quantum computation.

[0065] According to at least one embodiment, the quantum computer further comprises a cooling and / or readout system. The cooling and / or readout system is, for example, laser-based. The cooling system is configured to cool the ions so as to prepare the ions in a low-motion state and to trap the ions in their respective ground states. The readout system is configured to determine the state of each ion. For example, the ions are cooled and / or read out by irradiating a laser beam onto the ions or by scattered photons of the laser beam, respectively.

[0066] In the following, the quantum computer arrangement and the quantum computer will be described in more detail with reference to the accompanying drawings based on exemplary embodiments. The accompanying drawings are included to provide further understanding. In the accompanying drawings, elements of the same structure and / or function may be referred to by the same reference numerals. It should be understood that the embodiments shown in the accompanying drawings are illustrative representations and are not necessarily drawn to scale. In different drawings, when elements or components correspond to each other in terms of their functions, their description will not be repeated in each of the subsequent drawings. For the sake of clarity, the corresponding reference numerals may not appear in all drawings for the elements.

[0067] Figure 1 , Figure 5 and Figure 6 shows different exemplary embodiments of quantum computing arrangements,

[0068] Figure 2 and Figure 3 Detailed views of exemplary embodiments of Paul traps are shown in different views,

[0069] Figure 4 Another exemplary embodiment of a Paul trap is shown, and

[0070] Figure 7 An exemplary implementation of a quantum computer is shown.

[0071] Figure 1 A first exemplary embodiment of a quantum computing arrangement 1 is shown. The quantum computing arrangement 1 comprises a permanent magnet arrangement 2. The permanent magnet arrangement 2 comprises 16 permanently magnetized segments 3. The segments 3 surround a Paul trap 100. The Paul trap 100 is configured to trap a plurality of ions 6 along a predefined line 7 or trapping line 7, respectively. In this exemplary embodiment, the Paul trap 100 is a linear Paul trap for trapping ions 6 along a straight line 7. The straight line 7 defines the x-axis.

[0072] The permanent magnet arrangement 2 has the shape of a ring, wherein the Paul trap 100 is arranged at the center of the ring. The thickness of each segment 3 is, for example, about 100 μm. The ring spans the xy plane. Each segment 3 has the shape of a ring segment. The minimum distance between two opposing segments 3 (i.e., the inner ring diameter 2Ri) is about 10 cm. In addition, each segment 3 has an extension along the corresponding minimum distance of about 20 cm. Therefore, the outer diameter 2Ro of the permanent magnet arrangement 2 is about 50 cm. The edges of directly adjacent segments 3 facing each other have a distance between each other of, for example, about 10 mm.

[0073] In addition, each segment 3 has Figure 1 4 is depicted as an arrow in the segments 3 in FIG. 4 . For example, the segments 3 are each formed of NdFeB N52. The magnetization directions 4 of the segments 3 arranged at opposite regions relative to the center of the permanent magnet arrangement 2 point in opposite directions. The predefined line 7 passes through the center of the permanent magnet arrangement 2 and intersects the two opposite segments 3, wherein the magnetization directions 4 of the two segments 3 are parallel to the predefined line 7.

[0074] Each magnetization direction 4 encloses an angle with the predefined line 7. All these angles are formed differently from each other. For example, the angles of each two directly adjacent segments 3 differ from each other by 67.5°. The magnetization directions 4 are all in the xy plane.

[0075] Figure 1 The permanent magnet arrangement is a Halbach arrangement establishing a magnetic quadrupole field, wherein the magnitude of the magnetic field varies along the predefined line 7. In other words, the magnetic field has a magnetic field gradient along the predefined line 7. For example, each of the trapped ions arranged along the predefined line experiences a different magnetic field.

[0076] use Figure 1 The permanent magnet arrangement produces the following idealized magnetic flux density

[0077]

[0078] The residual magnetism B of each segment 3 R is, for example, 1 T. As can be extracted from this idealized magnetic flux density, the magnetic field is primarily a two-dimensional magnetic field concentrated in the xy plane constituting the magnetic field plane.

[0079] Figure 2 and Figure 3 Shows Figure 1 Detailed view of the Paul Trap 100. Figure 2 , the xy plane is indicated. Figure 3 is a plan view of the yz plane, that is, the view along the x-axis.

[0080] The Paul trap 100 comprises two end cap electrodes 40 and four radial electrodes 20, 30. Two radial electrodes 20 arranged diagonally opposite to each other on different sides of the magnetic field plane BP (xy plane) are RF electrodes supplied with an alternating voltage during operation. The other two diagonally opposite radial electrodes 30 are DC electrodes, which operate at a constant potential, such as ground.

[0081] The end cap electrodes 40 are operated at a static potential. Figure 2 , the potential V(x, 0, 0) along the x-axis generated by the Paul well 100 is shown.

[0082] Figure 3 The potentials on the y-axis and z-axis generated by the Paul trap 100 are shown. At time t1, the potential V(0, y, 0, t1) along the y-axis is attractive. At this time t1, the potential V(0, 0, z, t1) along the z-axis is repulsive or defocused, respectively. At time t2, i.e., after half an RF cycle, the potential V(0, 0, z, t2) along the z-axis is attractive. Along the y-axis, the potential V(0, y, 0, t2) is repulsive or defocused, respectively. These alternating potentials in the y-direction and the z-direction are used to form an attractive pseudo-potential so that the ion 6 is eventually trapped in the radial direction.

[0083] In summary, due to the electric potentials in different directions, a potential well W is formed to trap the ion 6. Figure 2 As shown, the ions 6 in the potential well W are arranged into a linear ionic crystal 6a.

[0084] Figure 2 and Figure 3 The magnitude of the electric field established by the permanent magnet arrangement 2 (i.e. the magnitude of the magnetic flux density |B|) is also indicated. It can be seen that the magnitude of the magnetic flux density |B| varies in the x-direction and in the y-direction, i.e. along the magnetic field plane BP. At the center of the magnetic field, the magnitude of the magnetic field is 0.

[0085] Figures 1 to 3 The ion 6 shown in is for example 171 Yb + ions. The distance d of directly adjacent trapped ions is about 3 μm. The degeneracy of the excited quantum state is resolved by the magnetic field generated by the permanent magnet arrangement 2. The energy for the π transition from the base quantum state to the excited m=0 quantum state depends weakly on the magnetic field experienced by the ion. Likewise, the σ transition from the base quantum state to the excited m=±1 quantum state depends weakly on the magnetic field experienced by the ion. ± The energy of the transition depends on the magnetic field experienced by the ions. Since the magnitude of the magnetic field depends on the position of the ions 6 along the predefined line 7, the energy of the transition depends on the position along the predefined line 7. For example, for every two adjacent ions 6, σ ±The difference in frequency of the transitions is at least 1 MHz and at most 100 MHz. Furthermore, for every two adjacent ions 6, the difference in frequency of the π transitions is at least 0.001 MHz and at most 10 MHz.

[0086] Furthermore, due to the form of the potential well along the predefined line 7 and the magnetic field provided by the permanent magnet arrangement 2, the equilibrium position of the ions 7 depends on their respective quantum states. Thus, an effective spin-spin coupling between the ions 6 due to the Coulomb interaction is achieved. This allows the quantum states of the ions 6 to be entangled.

[0087] In particular, the coupling strength between two directly adjacent trapped ions 6 depends on the square of the magnetic field gradient. In addition, the relaxation time, in particular the spin relaxation time T2, is inversely proportional to the decoherence rate. Therefore, in order to provide multi-qubit gates, the magnetic field gradient must be relatively high to provide a large number of gates in a given time. This can be achieved using the permanent magnet arrangement described herein.

[0088] Figure 4 Another exemplary embodiment of the Paul trap 100 is shown, wherein the end cap electrodes 40 are part of the yoke structure 60. The yoke structure 60 is configured to increase the magnetic field along the predefined line 7 in the region where the ions 6 are trapped. Each of the end cap electrodes 40 forms an elongated portion of the yoke structure 60. For example, the end cap electrodes 40 are made of a soft magnetic material such as Made of 50.

[0089] Figure 5 Another exemplary embodiment of a quantum computing arrangement 1 or a Paul trap 100, respectively, is shown. In contrast to the previous exemplary embodiments, the permanent magnet arrangement 2 is not separated from the Paul trap 100, but the Paul trap 100 itself forms the permanent magnet arrangement 2. This is achieved by different electrodes 20, 30, 40 forming a segment 3 of the permanent magnet arrangement 2. Each electrode 20, 30, 40 is made of a ferromagnetic material and has a magnetization direction 4. The magnetization directions 4 of at least some of the electrodes 20, 30, 40 are different from each other, thereby establishing a magnetic field in which the magnitude of the magnetic field changes along a predefined line 7.

[0090] exist Figure 6 In the exemplary embodiment of , the permanent magnet arrangement 2 surrounds the Paul trap 100 in the form of a polygonal outline. Each segment 3 has a square form. Adjacent segments 3 are rotated relative to each other.

[0091] As in Figure 6 As can also be seen in FIG. 1 , the Paul trap 100 is arranged in the chamber 10 and the chamber 10 is surrounded by the permanent magnet arrangement 2. The chamber 10 is, for example, an ultra-high vacuum chamber.

[0092] Figure 71 shows an exemplary embodiment of a quantum computer 8. The quantum computer 8 comprises a quantum computing arrangement 1 according to one of the exemplary embodiments described herein. A Paul trap 100 is connected to components of the quantum computer 8 via a chamber 10 by a plurality of connections 11. For example, the connections 11 connect the Paul trap 100 with external control electronics 12 and a classical computer 13.

[0093] The quantum computing arrangement 1 is configured to capture, manipulate and measure trapped ions. To this end, in addition to any components of the Paul trap 100 and the permanent magnet arrangement 2, the quantum computing arrangement 1 may also include an optical guide and / or internal electronic devices including electronic devices. The electronic devices may include circuits, integrated electronic devices, power supplies and / or detectors (e.g., photon detectors and / or charge detectors), controllers, etc. Exemplarily, internal electronic devices are provided for preprocessing. For example, these components allow the corresponding states of the ions to be measured and allow the ions to be gated. Therefore, the quantum computing arrangement 1 is configured to capture ions and is configured to perform operations and measurements on the trapped ions.

[0094] The Paul trap 100 is installed in a chamber 10, wherein the chamber 10 may be an ultra-high vacuum chamber, an extremely high vacuum chamber and / or a cryostat. The permanent magnet arrangement 2 may be arranged outside the chamber 10. In this case, the permanent magnet arrangement 2 surrounds the chamber 10. Alternatively, the permanent magnet arrangement 2 may be arranged inside the chamber 10 (not shown here).

[0095] The quantum computing arrangement 1, in particular the Paul trap 100, is connected to external electronics 12 via a connection 11. The external electronics 12 may be at least partially inside the chamber 10 and at least partially outside the chamber 10. Furthermore, the external electronics 12 is connected to a classical computer 13.

[0096] The external electronic device 12 includes, for example, an analog-to-digital converter and a signal generator such as a radio frequency generator, a microwave signal generator, a low frequency signal generator and / or a DC signal generator. In addition, the external electronic device 12 may include transistor-transistor logic TTL.

[0097] Additionally, the external electronics 12 may also include at least one laser-based system configured to cool the trapped ions. Additionally, the laser-based system may be configured to excite specific states of the trapped ions and / or read out specific states of the ions.

[0098] For example, the classical computer 13 is configured to provide and receive digital signals. The digital signals correspond to control signals for the operation of the qubits / ions and to measurement signals corresponding to the states of the qubits.

[0099] The external electronics 12 is in particular configured to convert digital signals into analog signals, and to convert analog signals into digital signals. Thus, the external electronics 12 is configured to provide the converted analog signals for manipulating the ions (qubits) to the quantum computing arrangement 1. Furthermore, the external electronics 12 is configured to provide the measured analog signals from the quantum computing arrangement 1 to the classical computer 13, or to process such signals to directly initiate some response signals generated by the control electronics 12.

[0100] The classical computer 13 is exemplarily configured to be provided with a specific algorithm, i.e. a predetermined quantum calculation that solves a specific problem. The classical computer 13 is then configured to convert the compiled code corresponding to the algorithm into commands for the quantum computing arrangement 1. The commands are then forwarded to the quantum computing arrangement 1 via the external control electronics 12. Furthermore, the classical computer 13 is configured to receive measurement results of the specific algorithm.

[0101] For example, all components of quantum computer 8 , in particular all electronic components of quantum computer 8 , are synchronized, for example, via an atomic clock reference.

[0102] The present invention is not limited to the description of the exemplary embodiments. Rather, the present invention covers any novel features and any combination of features, even if the feature or the combination itself is not explicitly indicated in the claims or exemplary embodiments, the present invention also specifically includes any combination of features in the claims.

[0103] Reference numerals list

[0104] 1 Quantum computing arrangement

[0105] 2. Permanent magnet arrangement

[0106] 3 segments

[0107] 4 Magnetization direction

[0108] 6 Ions

[0109] 6a Ionic crystals

[0110] 7 Predefined lines

[0111] 8 Quantum Computers

[0112] Room 10

[0113] 11. Connect

[0114] 12 Control electronics

[0115] 13 Classical Computers

[0116] 20 RF electrode

[0117] 30 DC electrode

[0118] 40 End cap electrode

[0119] 60 Yoke structure

[0120] 100 Paul Trap

[0121] d Distance

[0122] Ri inner radius

[0123] Ro outer radius

[0124] BP magnetic field plane

[0125] W potential well

[0126] V(x, y, z) potential

[0127] B(x, y, z) magnetic flux density

Claims

1. A quantum computing arrangement (1), comprising: - a permanent magnet arrangement (2) comprising a plurality of permanently magnetized segments (3), wherein: - the quantum computing arrangement (1) is configured to implement a Paul trap (100) for trapping ions (6) along a predefined line (7), - each segment (3) has a magnetization direction (4), The segments (3) are arranged such that the magnetization directions (4) of at least some of the segments (3) differ from one another and such that a magnetic field is established, the magnitude of which varies along the predefined line (7).

2. A quantum computing arrangement (1) according to claim 1, wherein - The segments (3) are arranged in a Halbach arrangement.

3. A quantum computing arrangement (1) according to claim 1 or 2, -in, The permanent magnet arrangement (2) surrounds the Paul trap (100) in the form of a ring or in the form of a polygonal outline.

4. A quantum computing arrangement (1) according to any one of the preceding claims, wherein: - at least some electrodes (20, 30, 40) of the Paul trap (100) are formed by segments (3) of the permanent magnet arrangement (1).

5. A quantum computing arrangement (1) according to any one of the preceding claims, wherein: - The Paul trap (100) is a linear Paul trap for trapping ions along a predefined straight line (7).

6. A quantum computing arrangement (1) according to any one of the preceding claims, further comprising: - a yoke structure (60) for increasing the magnetic field and / or the variation of the magnitude of the magnetic field established by the permanent magnet arrangement (2) along the predefined line (7).

7. A quantum computing arrangement (1) according to claim 6, wherein The yoke structure (60) is at least partially formed by the end cap electrodes (40) of the Paul trap (100).

8. A quantum computing arrangement (1) according to claim 6 or 7, wherein: - The yoke structure (60) comprises a soft magnetic material.

9. A quantum computing arrangement (1) according to any one of the preceding claims, further comprising: - a vacuum chamber (10) in which the ions (6) are trapped during operation, wherein: - The permanent magnet arrangement (2) is arranged outside the vacuum chamber (10).

10. A quantum computing arrangement (1) according to any one of the preceding claims, wherein: - the permanent magnet arrangement (2) creates a substantially two-dimensional magnetic field, which is mainly concentrated in the magnetic field plane (BP), - said predefined line (7) extends parallel to said magnetic field plane (BP).

11. A quantum computing arrangement (1) according to claim 10, wherein: - The RF electrodes (20) of the Paul trap (100) are arranged outside the magnetic field plane (BP) and on different sides of the magnetic field plane (BP).

12. A quantum computing arrangement (1) according to claim 10 or 11, wherein: - The end cap electrodes (40) of the Paul trap (100) are arranged in the magnetic field plane (BP).

13. A quantum computing arrangement (1) according to any one of claims 10 to 12, wherein: - said segment (3) is arranged in said magnetic field plane (BP).

14. A quantum computing arrangement (1) according to any one of the preceding claims, wherein: The Paul trap (100) is configured as follows: - Capture 171 Yb + ions so that during operation, - the minimum distance (d) of directly adjacent trapped ions (6) is at least 0.1 μm and at most 30 μm, and - The trapped ions (6) each have σ ± transition, at the σ ± The magnetic quantum number changes during the transition, where the σ between directly adjacent trapped ions (6) ± The frequency difference of the transitions is at least 100 kHz and at most 100 MHz, and / or The trapped ions (6) each have a π transition in which the magnetic quantum number does not change, wherein the frequency difference of the π transitions between directly adjacent trapped ions (6) is at least 1 kHz and at most 10 MHz.

15. A quantum computing arrangement (1) according to any one of the preceding claims, wherein: - the edges of the segments (3) arranged at opposite areas and facing each other have a minimum distance (2Ri) from each other of at least 10 μm and at most 100 cm, - Each segment (3) has an extension along a respective minimum distance of at least 10 μm and at most 100 cm.

16. A quantum computer (8), comprising: - A quantum computing arrangement (1) according to any one of claims 1 to 15, configured for performing quantum computing.

17. The quantum computer (8) according to claim 16, further comprising: - Laser based cooling and / or readout systems.

Images