Component for Reading Out the States of Qubits in Quantum Dots

Abstract

An electronic component (10) is formed by a semiconductor component or a semiconductor-like structure having gate electrode assemblies (16, 18), for reading out the quantum state of a qubit in a quantum dot (42). The electronic component (10) comprises a substrate (12) having a two-dimensional electron gas or electron hole gas. Electrical contacts connect the gate electrode assemblies (16, 18) to voltage sources. The gate electrode assemblies (16, 18) have gate electrodes (20, 22, 30, 32, 34, 38, 40), which are arranged on a surface (14) of the electronic component (10), for producing potential wells (46, 48, 62, 64, 66) in the substrate (12).

Claims

1.-13. (canceled)

14. An electronic component (10), which is formed by a semiconductor component or a semiconductor-like structure having gate electrode assemblies (16, 18), for reading out a quantum state of a qubit in a quantum dot (42), comprising: a substrate (12) with a two-dimensional electron gas or electron hole gas; electrical contacts for connecting the gate electrode assemblies (16, 18) to voltage sources; gate electrode assemblies (16, 18) having gate electrodes (20, 22, 30, 32, 34, 38 ,40), which are arranged on a surface (14) of the electronic component (10), for producing potential wells (46, 48, 62, 64, 66) in the substrate (12); parallel electrode fingers (26, 28) being part of the gate electrodes (20, 22) of the gate electrode assemblies (16, 18), wherein in a first gate electrode assembly (16), the electrode fingers (26, 28) are interconnected in a periodically alternating manner, which causes an almost continuous movement of the potential well (46) through the substrate (12), whereby a first quantum dot (42) is transported together with this potential well (46), and wherein the electrode fingers of a second gate electrode assembly (18) form a static potential well (48, 62) in which a second charge carrier (58) with a known quantum mechanical state is provided; and a sensor element (36) for detecting changes in the charge, which detects the charge in the static potential well (48, 62), wherein the first quantum dot (42) is transported to a second quantum dot (44).

15. The electronic component (10) according to claim 14, further comprising a magnetic field generator for generating a gradient magnetic field in order to initialize the quantum mechanical state of the quantum dot of the static potential well (48, 62).

16. The electronic component (10) according to claim 14, wherein the second gate electrode assembly (18) comprises two further gate electrodes (38, 40), which together form a static double potential well (62), wherein each of the static potential wells (64, 66) has a quantum dot (44, 60) with different quantum mechanical states.

17. The electronic component (10) according to claim 14, wherein a gate electrode assembly (16) for the moved potential well (46) comprises two parallel gate electrodes (26, 28), which form a channel-like structure.

18. The electronic component (10) according to claim 14, wherein the substrate (12) of the electronic component (10) comprises gallium arsenide (GaAs) and/or silicon germanium (SiGe).

19. The electronic component (10) according to claim 14, wherein the respectively interconnected gate electrodes (20, 22) for the moved potential well (46) are configured such that a periodic and/or phase-shifted voltage can be applied to them.

20. The electronic component (10) according to claim 14, wherein every third electrode finger (26, 28) is connected to a gate electrode (20, 22) for the movable potential well (46).

21. The electronic component (10) according to claim 14, further comprising means of connection for connecting to a qubit of a quantum computer.

22. The electronic component (10) according to claim 14, further comprising a magnetic field generator for a switchable magnetic field.

23. A method for the electronic component (10) according to claim 14, comprising the following method steps: introducing a first charge carrier (58) into the quantum dot (44) of the static potential well (48, 62); initializing the quantum mechanical state of the charge carrier (58) of the first quantum dot (44); detecting the charge of the first quantum dot (44) by the sensor element (36); introducing a qubit of the second quantum dot (42) into the movable potential well (46); bringing the movable potential well (46) towards the static potential well (48, 62); transferring the charge from quantum dot (42) into quantum dot (44); detecting the charge by the sensor element (36) in the static potential well (48, 62); and checking the change in charge in the static potential well (48, 62).

24. The method according to claim 23, wherein the static potential well (62) is formed as a double potential well (64, 66), each of which is occupied by charge carriers with different quantum mechanical states.

25. The method according to claim 23, further comprising: applying a phase-shifted voltage to the interconnected gate electrodes (20, 22) for the movable potential well (46), which causes an almost continuous movement of the potential well (46) through the substrate (12), and thereby transporting a quantum dot (42) with this potential well (46).

26. The method according to claim 23, further comprising connecting every fourth gate electrode (20, 22) for the movable potential well (46) to one other, and applying a periodic voltage to the every fourth gate electrodes (20, 22).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows a schematic top view of the electronic component for reading out the quantum state of a quantum dot with a static potential well.

[0044] FIG. 2 shows a schematic diagram of the sequence of an electronic component for reading out the quantum state of a quantum dot with a static potential well.

[0045] FIG. 3 shows a schematic top view of the electronic component for reading out the quantum state of a quantum dot with a static double potential well.

[0046] FIG. 4 shows a schematic diagram of the sequence of an electronic component for reading out the quantum state of a quantum dot with a static double potential well.

DETAILED DESCRIPTION

[0047] FIG. 1 shows a first exemplary embodiment of an electronic component 10, which is formed from a semiconductor heterostructure. The structures of the component are preferably nanoscale structures. Undoped silicon germanium (SiGe) is used as the substrate 12 for the electronic component 10. The electronic component 10 is designed in such a manner that it comprises a two-dimensional electron gas (2DEG). Gate electrode assemblies 16, 18 are provided on a surface 14 of the substrate 12.

[0048] The gate electrode assembly 16 has two gate electrodes 20, 22. The individual gate electrodes 20, 22 are electrically isolated from one another in a suitable manner with insulating layers 24. The gate electrode assemblies 16, 18 are provided in layers, wherein the insulating layer 24 is provided between each gate electrode 20, 22. The gate electrodes 20, 22 further comprise electrode fingers 26, 28, which are arranged parallel to another on the surface 14 of the substrate 12.

[0049] The gate electrode assemblies 16, 18 are supplied with a suitable voltage via electrical connections. By suitably applying sinusoidal voltages to the gate electrodes 20, 22 of the gate electrode assembly 16, a potential well is generated in the substrate 12. A quantum dot or charge carrier trapped in this potential well can thus be transported through the substrate in this manner. The potential well is transported longitudinally through the substrate through suitable control of the electrode fingers 26, 28 with sinusoidal voltages. The quantum dot or charge carrier confined in such a potential well can be transported with this potential well over a greater distance in the two-dimensional electron gas of the substrate 12 made of SiGe without experiencing a quantum mechanical change of state.

[0050] The gate electrode assembly 16 forms a region in which a quantum dot can be transported by means of a potential well. The gate electrode assembly 18, on the other hand, forms a static potential well. The gate electrode assembly 18 comprises for this purpose barrier gate electrodes 30, 32 and a pump gate electrode 34, which can set a quantum dot or a charge carrier in motion or in oscillation. The pump gate electrode 34 is arranged between the barrier gate electrodes 30, 32. The gate electrodes 30, 32, and 34 are also separated from one another by an insulating layer 24.

[0051] The barrier gate electrode assembly includes a sensor element 36 for detecting changes in charge. The sensor element 36 detects the charge present in the static potential well. The potential well is generated by the gate electrode assembly 18.

[0052] FIG. 2 shows a schematic diagram of the sequence for reading out a quantum state of a qubit in a quantum dot 42. The diagram shows a section of the electronic component 10 so that only the electrode fingers 26, 28; the barrier gate electrodes 30, 32; and the pump gate electrodes 34 are visible in the section. Sequences from A to C of the positions of the potential wells 46, 48 in the substrate 12 are shown below this to explain the function. The electrode fingers 26, 28 of the gate electrode assembly 16 form the movable potential well 46 through the substrate 12. The movement of the quantum dot 42 in the potential well 46 is effected by appropriately interconnecting the electrode fingers 26, 28. The electrode fingers 26, 28 of the gate electrode assembly 16 provided for this purpose are periodically and alternately interconnected, which effects an almost continuous movement of the quantum dot 42 in the potential well 46 through the substrate 12.

[0053] The electronic component 10 is based on the physical Pauli Exclusion Principle, which states that an electron level can never be occupied by electrons with the same spin. By means of the gate electrodes 30, 32, a static potential well 48 is generated on the one hand and, on the other hand, a movable potential well 46 is generated by means of the gate electrodes 26, 28. A quantum dot 42 is introduced into the static potential well 48, the quantum mechanical state of which is known in one level, which in the case of an electron is the spin. The quantum dot is oriented with the pump gate electrode 40, for example with spin up, as illustrated here. A further quantum dot 44 of the same level is introduced into the static potential well 48 by means of the movable potential well 46. Arrow 50 indicates the direction of transport of the quantum dot 44 with movable potential well 46. If the quantum mechanical states are different, then the level is filled. The level can be filled by tunneling, which is symbolized by arrow 52.

[0054] In the event that a quantum dot has been added, the sensor element 36 detects a change in charge in this level. If the quantum mechanical states of the quantum dots 42, 44 are the same, then the level cannot accept another charge carrier 58. The quantum mechanical state therefore does not change in this level. As a result, it is possible to determine the quantum mechanical state of the quantum dot 42 introduced.

[0055] FIG. 3 shows a further exemplary embodiment of an electronic component 10, which is again formed from a semiconductor heterostructure. The structures of the component are preferably nanoscale structures. Undoped silicon germanium (SiGe) is used as the substrate 12 for the electronic component 10. The electronic component 10 is designed in such a manner that it comprises a two-dimensional electron gas (2DEG). The gate electrode assemblies 16, 18 are provided on the surface 14 of the substrate 12.

[0056] The gate electrode assembly 16 has two gate electrodes 20, 22. The individual gate electrodes 20, 22 are electrically isolated from one another in a suitable manner with insulating layers 24. The gate electrodes 20, 22 of the gate electrode assembly 16 are provided for this purpose in layers, wherein the insulating layer 24 is provided between each gate electrode 20, 22 of the gate electrode assembly 16. The gate electrodes 20, 22 further comprise the electrode fingers 26, 28, which are arranged parallel to another on the surface 14 of the substrate 12.

[0057] The gate electrode assemblies 16, 18 are supplied with a suitable voltage via electrical connections. By suitably applying sinusoidal voltages to the gate electrodes 20, 22 of the gate electrode assembly 16, a movable potential well is generated in the substrate 12. A quantum dot 42 or charge carrier trapped in this potential well can thus be transported through the substrate in this manner. The potential well is transported longitudinally through the substrate through suitable control of the electrode fingers 26, 28 with sinusoidal voltages. The quantum dot 42 confined in such a potential well can be transported with this potential well over a greater distance in the two-dimensional electron gas of the substrate 12 made of SiGe without experiencing a quantum mechanical change of state.

[0058] The gate electrode assembly 18 forms a static double potential well. The gate electrode assembly 18 comprises for this purpose barrier gate electrodes 30, 32, 38 and, in addition to the pump gate electrode 34, another pump gate electrode 40, which can set a quantum dot or a charge carrier in motion or in oscillation. The pump gate electrodes 34, 40 are alternately arranged between the barrier gate electrodes 30, 32, and 38.

[0059] The sensor element 36 for detecting changes in charge is adjacent to the barrier gate electrode assembly 18. The sensor element 36 detects the charge present in the static double potential well. The double potential well is generated by the gate electrode assembly 18.

[0060] FIG. 4 shows a schematic diagram of the sequence for reading out a quantum state of a qubit in the quantum dot 42. The diagram shows a section of the electronic component 10 so that only the electrode fingers 26, 28; the barrier gate electrodes 30, 32, 38; and the pump gate electrodes 34, 40 are visible in the section. Sequences from A to F of the positions of the potential wells 46, 64, 66 in the substrate 12 are shown below this to explain the function. The electrode fingers 26, 28 of the gate electrode assembly 16 form the movable potential well 46 through the substrate 12. The movement of the potential well 46 is effected by appropriately interconnecting the electrode fingers 26, 28. The electrode fingers 26, 28 of the gate electrode assembly 16 provided for this purpose are periodically and alternately interconnected, which effects an almost continuous movement of the potential well 46 through the substrate 12.

[0061] The electronic component 10 is based on the physical Pauli Exclusion Principle, which states that an electron level can never be occupied by electrons with the same spin. By means of the gate electrodes 30, 32, and 38, a static double potential well 62 is generated on the one hand and, on the other hand, the movable potential well 46. A charge carrier 58 is introduced into a first potential well 64 of the static double potential well 62. Two charge carriers 58 are split with the pump gate electrodes 34, 40, for example with the aid of a gradient magnetic field. A split charge carrier 60 tunnels into a second static potential well 66. A further quantum dot 42 is introduced into the second static potential well 66 of the double potential well 62 of the same level by means of the movable potential well 46. The arrow 50 indicates the direction of transport of the quantum dot 42 with the movable potential well 46. The quantum dot 60 of the second static potential well 66 exchanges with the quantum dot 42 of the movable potential well 46. The quantum mechanical state with the movable potential well 46 is known. The quantum dot 42, provided it has the same spin as the quantum dot 60, tunnels into the first static potential well of the double potential well 62. The sensor element 36 does not detect any change in charge. If the quantum mechanical states of the quantum dots 60 and 42 differ, then a change in charge is detected. The level can be filled by tunneling, which is symbolized by arrow 52.

LIST OF REFERENCE SIGNS

[0062] 10 Electronic component

[0063] 12 Substrate

[0064] 14 Surface

[0065] 16 Gate electrode assembly

[0066] 18 Gate electrode assembly

[0067] 20 Gate electrodes

[0068] 22 Gate electrodes

[0069] 24 Insulating layer

[0070] 26 Electrode fingers

[0071] 28 Electrode fingers

[0072] 30 Barrier gate electrode

[0073] 32 Barrier gate electrode

[0074] 34 Pump gate electrode

[0075] 36 Sensor element

[0076] 38 Barrier gate electrodes

[0077] 40 Pump gate electrode

[0078] 42 Quantum dot

[0079] 44 Quantum dot

[0080] 46 Moved potential well

[0081] 48 Static potential well

[0082] 50 Arrow (transportation)

[0083] 52 Arrow (tunneling)

[0084] 58 Charge carrier

[0085] 60 Split quantum dot

[0086] 62 Double potential well

[0087] 64 First static potential well

[0088] 66 Second static potential well