QUANTUM DEVICE

Description

Domaine de l'invention

[0001] The invention relates to a quantum device. The field of the invention is that of quantum devices, and more particularly of quantum information processing. Etat de la technique

[0002] A quantum system is based on the use of a multi-level quantum state. In many fields, such as electronics, quantum systems can have more than two levels, which is similar to classical electronics where N-value logic can be used, with N greater than 2. A quantum system with different levels can be described by considering only its first two energy levels. In particular, quantum computing is based on the use of a measurable two-level quantum state as an information carrier, called a qubit or quantum bit, and the laws of quantum mechanics (superposition, entanglement, measurement) to execute algorithms. A quantum device, or computer, allows manipulation of the quantum state of these qubits, notably for the purpose of performing operations.Unlike a so-called classical electronic or computer machine (operating with two voltage levels defined as corresponding to binary states 0 and 1), a quantum device approaches an analog machine, in the sense that the quantum state of the qubits can take an infinite number of values.

[0003] A system using an electron or a quasiparticle with spin % can be used to materialize a qubit, called a spin qubit, the two levels corresponding to the two possible spin orientations. Spin qubits can be formed in semiconductors, advantageously silicon. Semiconductor technologies are being studied for the realization of spin qubits due to their high integration potential, similar to classical electronics. Electrons or holes are individually confined in quantum wells maintained at cryogenic temperatures (below 1 Kelvin (K)) in a cryostat and fabricated within nanometer-sized confinement structures defined electrostatically and, in the case of silicon, with an architecture similar to that of MOSFETs. These confinement structures correspond to quantum dots.A quantum dot behaves like a potential well confining one or more elementary charges (electrons or holes) in a region of semiconductor.

[0004] Reading a spin qubit is performed using another quantum dot, called the read quantum dot, coupled to the read quantum dot of the spin qubit to be read. These two quantum dots form two potential wells separated by a potential barrier. Each quantum dot has an electrostatic control grid arranged on a first semiconductor region in which the potential wells of the quantum dots are formed. The potential wells are arranged between second semiconductor regions forming charge carrier reservoirs, called the source and drain by analogy with MOSFET technology. A quasiparticle can be a hole or an electron. The spin of the quasiparticle in the read quantum dot is used as the "reference spin," while the spin of the quasiparticle in the read quantum dot is measured after it has been manipulated.

[0005] Several methods exist for reading spin qubits. The first involves measuring the capacitance between two quantum dots, which reflects their relative states. The second involves measuring the conductance of an electrometer, this conductance reflecting the state of the qubit near the electrometer. See Vandersypen 2016 for more information.

[0006] The first method for reading spin qubits involves measuring the capacitance between the quantum dot of the qubit to be read and the readout quantum dot, which represents their relative states. This is typically done using a reflectometry device. A high-frequency signal (for example, between 100 MHz and a few GHz) is sent to the grid of the readout quantum dot from test instruments located at room temperature, outside the cryostat containing the quantum dots. The signal is reflected and then demodulated. An inductor is placed at the end of the line at the qubit to create an LC resonator composed of this inductor, a parasitic capacitance, and the quantum capacitance Cq formed by the qubit. When the value of Cq changes, the phase and amplitude of the reflected signal change, which can be detected by the room-temperature measuring instruments.It is thus possible to know the relative state (parallel or anti-parallel) of the spin of the electron present in the reading quantum dot as a function of the spin state of the electron present in the quantum dot of the qubit intended to be read.

[0007] With this first reading method, it is necessary either to extend from the cryostat a number of wires equal to the number of qubits to be excited, which becomes impossible when the number of qubits is large, for example, more than 1000, or to send several signals at different frequencies through the same wire and discriminate these frequencies using LC resonators placed at cryogenic temperature. In this latter solution, it is therefore necessary that the resonant frequency of the LC resonator associated with each qubit be calibrated and different for each resonator.There is therefore a compromise between frequency spacing between each qubit (defined by the quality factor of the LC resonators, because the higher the quality factor, the greater the number of qubits addressed by a single line can be), area taken by the inductances (the smaller an inductance, the lower its quality factor) and time taken by the reading (inversely proportional to the quality factor of the LC resonator) to be found.

[0008] Furthermore, with this first reading method, the use of magnetic nuclei to facilitate inductance integration is limited by the strong static magnetic field required to induce spin in the quasiparticles, which saturates the magnetic permeabilities of the nuclei. Air inductors do not encounter this problem, but they occupy a much larger surface area, limiting their widespread use inside the cryostat.

[0009] Inter-inductance couplings can also pose new problems when simultaneously measuring qubits using several of these inductances excited by reflectometry signals.

[0010] The second method involves measuring the conductance of an electrometer coupled to the quantum dot of the qubit to be read. This conductance reflects the qubit's state. Indeed, due to the Zeeman effect (the separation of an atom's atomic energy level into several distinct energy sublevels under the influence of an external magnetic field), when the quasiparticle's spin is oriented upwards, it is necessarily in the "high" energy state (which we will call H). Conversely, if the quasiparticle's spin is oriented downwards, it is in a "low" energy state (which we will call L). By placing the energy level of the reservoir near a quantum dot between H and L, the quasiparticle will tend to escape the quantum dot when it is in the H state and remain in the quantum dot when it is in the L state (Pauli exclusion).It is thus possible to convert the spin of the quasiparticle into charge information (whether or not the quasiparticle is present in the quantum dot), a conversion commonly called "spin-to-charge conversion." This charge information can be read by an electrometer such as a single-electron transistor (SET) or a quantum point contact (QPC), whose conductance varies depending on its electrostatic environment. For more information on QPCs, see Reilley 2007.

[0011] With this second method, the spin variation of the quasiparticle is converted into a charge variation of the quantum dot (thanks to Pauli exclusion), which leads to a change in the conductance of the electrometer. This, in turn, results in a change in the current flowing through the electrometer. This current can then be amplified by a transimpedance amplifier (TIA). Typically, this reading is taken with a TIA at room temperature connected to an electrometer.Therefore, this solution cannot be used to address a large number of qubits, such as an entire qubit matrix, because it would be necessary either to extend the cryostat by at least as many wires as there are qubits being addressed, which requires far too much space, or to place all the TIAs inside the cryostat, which is not feasible given the cooling capabilities of current cryostats (1W maximum for operation at 4K, or 1mW for operation at 100mK). Furthermore, the read speed of such a solution is limited by the capacitance of the wires (between 100 and 300 pF) required to charge the TIAs upstream of the room-temperature TIAs. The bandwidth of such a system could hardly exceed ten kHz.

[0012] One aim of the invention is to remedy at least one of the aforementioned drawbacks.

[0013] Another aim of the invention is a quantum device arranged to minimize the number of wires per spin qubit.

[0014] Another aim of the invention is to provide a quantum device that consumes less energy.

[0015] Another aim of the invention is to provide a more compact quantum device. Exposé de l'invention

[0016] At least one of the aforementioned objectives is achieved by a quantum device comprising: several spin qubits, each comprising at least one quantum dot; several electrometers, each being capacitively coupled to a potential well of at least one quantum dot of at least one of the spin qubits; and several injection-locked oscillators, each being coupled to at least one electrode of one of the electrometers and arranged to emit an oscillating signal, called an excitation signal, on at least one input electrode of the electrometer to which it is coupled, each excitation signal having a different frequency, characterized in that it also comprises an amplification circuit comprising at least one amplifier, said amplification circuit being coupled to the output of each electrometer and comprising an output, and in that said device comprises a feedback loop coupling the output of said amplification circuit to an input of each injection-locked oscillator and in which circulates an electrical signal, called the injection signal, comprising components at the frequencies of said excitation signals, each injection-locked oscillator being arranged to receive the injection signal and, depending on said injection signal, to maintain its excitation signal in a first operating state or to decrease its excitation signal in a second operating state.

[0017] According to these characteristics, the device according to the invention allows the reading of a plurality of spin qubits by using a single amplification circuit which may include only one amplifier, N electrometers as well as N injection-locked oscillators, with N greater than 1. Therefore, the device according to the invention allows the reading of a plurality of spin qubits while limiting the number of wires per spin qubit.

[0018] Furthermore, according to the invention, the output of the amplification circuit is connected to an input of the N injection-locked oscillators, allowing the injection signal to be injected into the injection-locked oscillators used to excite the electrometers. According to the invention, each injection-locked oscillator receives at its input an injection signal comprising all the components of the excitation signals of the device according to the invention, and at its output emits a single excitation signal. In particular, for each injection-locked oscillator, the presence of an injection signal at the resonant frequency, preferably with a suitable phase (generally in opposite phase), drastically reduces the amplitude of the oscillation of the injection signal emitted by the injection oscillator, whereas an injection signal at a different frequency has no effect on the operation of the injection oscillator in question.Each injection-locked oscillator thus alternately exhibits two operating states: the first state in which the excitation signal oscillates from an initial state, and the second state in which the injection signal is reduced. The device according to the invention therefore limits the number of electronic components used. Thus, in the device according to the invention, energy consumption and the space occupied by the electronic components are optimized, resulting in a compact device that consumes less energy than devices known according to the prior art.

[0019] An object of the invention is a quantum device comprising: several spin qubits, each comprising at least one quantum dot; several electrometers, each being capacitively coupled to a potential well of at least one quantum dot of at least one of the spin qubits; several injection-locked oscillators, each being coupled to at least one electrode of one of the electrometers and arranged to emit an oscillating signal, called an excitation signal, on at least one input electrode of the electrometer to which it is coupled, each excitation signal having a different frequency; an amplification circuit comprising at least one amplifier, said amplification circuit being coupled to the output of each electrometer and comprising an output, characterized in that said device comprises a feedback loop coupling the output of said amplification circuit to an input of each injection-locked oscillator and through which flows an electrical signal, called an injection signal;comprising components at the frequencies of said excitation signals, each injection-locked oscillator being arranged to receive the injection signal and, depending on said injection signal, to maintain its excitation signal in a first operating state or to decrease its excitation signal in a second operating state.

[0020] Another object of the invention is a method for reading several spin qubits, each comprising a quantum dot, said method using several electrometers, each being capacitively coupled to a potential well of at least one quantum dot of at least one of the spin qubits, several injection-locked oscillators, each being coupled to at least one electrode of one of the electrometers, an amplification circuit, said amplification circuit being coupled to the output of each electrometer and comprising at least one amplifier and one output, said method comprising: an emission by each injection-locked oscillator of an oscillating signal, called an excitation signal, on at least one input electrode of the electrometer to which it is coupled, each excitation signal having a different frequency, characterized in that said method further comprises: an injection of a signal, called an injection signal, into each injection-locked oscillator by a feedback loop coupling the output of said amplification circuit to the input of each injection-locked oscillator, the injection signal comprising components at the frequencies of said excitation signals, and for each injection-locked oscillator, a reduction or preservation of the excitation signal resulting from said injection signal. Brève description des dessins

[0021] The invention will be better understood and other advantages will become apparent upon reading the following description, given by way of example only, and with reference to the attached figures, among which: There FIGURE 1 is a schematic representation of a first example of a device according to the invention; The FIGURE 2 is a schematic representation of the first example of the device according to the invention when all the spin qubits are in a low state; The FIGURE 3 is a schematic representation of the first example of the device according to the invention when one of the spin qubits is in a high state; The FIGURE 4 is a schematic representation of the first example of the device according to the invention when the measurement means associated with the spin qubit in the high state is in a second operating state; The FIGURE 5 is a schematic representation of a first example of the device according to the invention when three spin qubits are in a high state; The FIGURE 6 is a schematic representation of the first example of the device according to the invention when the measurement means associated with the high-state spin qubits are in a second operating state; The FIGURE 7 is a schematic representation of a second example of a device according to the invention; The FIGURE 8 is an example of a measuring means used in a device according to the invention; The FIGURE 9 is an example of an amplification circuit used in a device according to the invention; The FIGURE 10 is another example of a measuring means used in a device according to the invention; The FIGURE 11 is an example of an injection-locked oscillator used in a device according to the invention; The FIGURE 12 is a schematic representation of a third example of a device according to the invention; and The FIGURE 13 is a schematic representation of a fourth example of a device according to the invention. FIGURE 14 is a schematic representation of a first example of a method according to the invention. Description détaillée des dessins

[0022] There FIGURE 1 is a schematic representation of a first example of a device 100. Device 100 is a quantum device 100 and includes: several spin qubits 102 each comprising at least one quantum dot, several electrometers 104 each being capacitively coupled to a potential well of at least one quantum dot of at least one of the spin qubits 102, several injection-locked oscillators 106, each being coupled to at least one electrode of one of the electrometers 104 and arranged to emit an oscillating signal, called an excitation signal 122, on at least one input electrode of the electrometer 104 to which it is coupled, each excitation signal 122 having a different frequency, an amplification circuit 108 comprising at least one amplifier 110, said amplification circuit 108 being coupled to the output of each electrometer 104 and comprising an output 112.

[0023] In this example, the system includes, in particular: four spin qubits, each numbered 102 1 , 102 2 , 102 3 , 102 4 , four electrometers, respectively called first electrometer 104 1 , second electrometer 104 2 , third electrometer 104 3 and fourth electrometer 104 4 , and four injection-locked 106 oscillators, respectively called first injection-locked oscillator 106 1 , second injection-locked oscillator 106 2 , third injection-locked oscillator 106 3 , and fourth injection-locked oscillator 106 4 .

[0024] Of course, in other variants of device 100, device 100 may include more or fewer of these components. For example, device 100 may include between 2 and 10,000 qubits.

[0025] The device 100 further includes a feedback loop 114 coupling the output 112 of the amplification circuit 108 to an input 116 of each injection-locked oscillator 106, and through which flows an electrical signal, called the injection signal 120, also denoted I 108. The injection signal 120 comprises components at the frequencies of said excitation signals 122. In the device 100, each injection-locked oscillator 106 is arranged to receive the injection signal 120 and, depending on said injection signal 120, to maintain its excitation signal 122 in a first operating state or to decrease its excitation signal 122 in a second operating state. In the example illustrated in FIGURE 1 The injection signal 120 is related to a current. In other variants, the injection signal can be a voltage. For more information on injection-locked oscillators, see Yoon 2004 or FR 3 089 724.

[0026] In the device 100 illustrated in FIGURE 1 The amplification circuit 108 comprises a single amplifier 110. In the embodiment illustrated in FIGURE 1 , the amplifier can be a transimpedance amplifier, also noted TIA or the amplification circuit 108 is arranged to perform current amplification.

[0027] Without limitation, the spin qubits of the device 100 can be spin qubits implemented in a semiconductor layer, for example silicon or germanium. The charges whose spin is to be read can be electrons or holes.

[0028] Furthermore, following this embodiment, the electrometers 104 of the device 100 may preferably comprise single-electron transistors (SETs). In this case, each electrometer 104 of the device 100 may comprise a gate, a source, and a drain. For example, the drain and gate of each electrometer 104 may form the input electrodes of the electrometers 104, while the sources of the electrometers 104 form the output electrodes of the electrometers 104. The sources of the electrometers 104 may be electrically connected to each other. Of course, in other, unillustrated variants, the electrometers 104 may comprise or be quantum point contacts (QPCs).

[0029] Following this example, each injection-locked oscillator 106 can be coupled to the grid of the corresponding electrometer 104. Thus, each excitation signal 122 is applied to the grid of the electrometer 104. In another variant, each injection-locked oscillator 106 can be coupled to the drain of the corresponding electrometer 104. The excitation signal sent to the drain of the electrometer can be more linear than a signal sent to the grid of the electrometer. The measurement accuracy can therefore be improved.

[0030] When the electrometers 104 correspond to QPCs, the excitation signals 122 are applied by injection-locked oscillators 106 to the input electrode of each of the QPC-type electrometers 104; this may be to the electrode on which a DC bias voltage is delivered.

[0031] Following the FIGURE 1 Each excitation signal 122 can be a sinusoidal signal, each with a different frequency. The excitation signal 122 can be related to a current. In the example illustrated in FIGURE 1 Each injection-locked oscillator 106 produces an excitation signal 122 comprising at least one frequency and one amplitude. The frequency of the excitation signal 122 is specific to each injection-locked oscillator 106, and the amplitude of the excitation signal 122 is a function of the spin qubit state.

[0032] As an example, the output signal from each injection-locked oscillator 106 can be noted as: I 106 i = A i sin 2 πf i t With the index i corresponding to the number of the injection-locked oscillator 106 and fi corresponding to the frequency of the injection-locked oscillator 106 numbered i, and A i the amplitude of the corresponding excitation signal 122. In this example, the amplitude A i exiting each electrometer 104 is a function of the state of the spin qubit positioned with respect to the corresponding electrometer 104. Without limitation, the excitation signal 122 1 delivered by the first injection-locked oscillator 106 1 can have a frequency f 1 equal to 10 MHz, the excitation signal 122 2 delivered by the second injection-locked oscillator 106 2 can have a frequency f 2 equal to 11 MHz, the excitation signal 122 3 delivered by the third injection-locked oscillator 106 3 can have a frequency f 3 equal to 13 MHz and the excitation signal 122 4 delivered by the fourth injection-locked oscillator 106 4 can have a frequency f 4 equal to 14 MHz.Thus, according to the . FIGURE 1 All excitation signals 122 comprise different frequencies. Furthermore, these frequencies are spaced far enough apart to avoid errors related to false alarms and / or non-detections. Typically, the spacing between frequencies can be on the order of 1 MHz, more commonly between 100 kHz and 10 MHz.

[0033] In device 100, all the output signals from the electrometers 104 are combined into one signal at the input of the amplification circuit 108. The signal at the input of the amplification circuit 108 is, by Kirchhoff's current law, a function of all the output signals from the different electrometers 104.

[0034] As an example, the signal at the input of the amplification circuit 108 is written I e , 108 = ∑ i = 1 N I 106 i = ∑ i = 1 N A i sin 2 πf i t With N corresponding to the total number of electrometers 104 present in the device 100 (in the case of the FIGURE 1 N is equal to 4), the index e referring to the input of the amplification circuit 108. Thus, the signal at the input of the amplification circuit 108 is a function of all the excitation signals 122. The signal at the input of the amplification circuit 108 therefore contains all the components of all the excitation signals 122 of the device 100. Consequently, the signal at the input of the amplification circuit 108 contains the state information of each spin qubit. In the example illustrated in FIGURE 1 , the signal at the input of the amplification circuit 108 is a spectrum which includes a line associated with each excitation signal 122. Each line of the spectrum of the signal at the input of the amplification circuit 108 has an amplitude that is a function of the state of the corresponding spin.

[0035] As an example, the device 100 further includes a cryostat including a chamber configured to be maintained at a temperature less than or equal to 4 Kelvins (K) and in which are arranged at least the spin qubits, the electrometers 104, the injection-locked oscillators 106, and the amplification circuit 108 and, if necessary, biasing circuits.

[0036] In the device according to the invention, the spin information for each spin qubit is obtained by analyzing the excitation signal 122 at the output of each injection-locked oscillator 106. The injection signal 120 entering each injection-locked oscillator 106 carries demultiplexed information in the locked oscillators 106 used for the initial excitation. Thus, the device 100 relies on the use of N electrometers 104, N injection-locked oscillators 106, and an amplification circuit 108 comprising, in the illustrated example, a single amplifier 110, used for reading N spin qubits, where N is an integer greater than 1.Such an arrangement also eliminates the need for a multitude of demultiplexing chains that might be required to retrieve information about the spin of each qubit (for example, N demultiplexing chains). These chains could consist of several components such as analog-to-digital converters, mixers, integrators, and / or comparators. Consequently, the device according to the invention is less bulky, and the elimination of demultiplexing chains reduces the energy consumption of each component, thus limiting the overall energy consumption of the device.

[0037] There FIGURE 2 is a schematic representation of device 100 when all the spin qubits of device 100 are in the low state.

[0038] In device 100, the conductance associated with each electrometer 104 varies according to the state of the spin qubit to which the electrometer 104 is coupled. For example, when the spin qubit is in a low state, the conductance of an electrometer 104 can be on the order of tens of nanosiemens (nS), corresponding to a current on the order of nanoamperes (nA), whereas the conductance of an electrometer 104, when the spin qubit is in a low state, can be on the order of tens of picosiemens (pS), corresponding to a current on the order of picoamperes (pA). The output signal of each electrometer depends on the state of the spin qubit.

[0039] As an example, the excitation signal 122 passing through an electrometer 104 can be on the order of pA if an electron present in the quantum dot of the spin qubit has its spin oriented downwards, and on the order of nA if the electron present in the quantum dot of the spin qubit has its spin oriented upwards.

[0040] The spin qubits illustrated in FIGURE 1 are all in a low state. Therefore, the amplitudes associated with each spin qubit are on the order of picoamperes (pA) and thus small compared to the high state of spin qubits, which can be on the order of nA. Thus, the signal at the input of the amplification circuit 108 is on the order of pA.

[0041] The amplification circuit 108 is arranged to amplify the signal at its input. In the example illustrated in FIGURE 2 The amplification circuit is configured to perform negative amplification. This characteristic simplifies the implementation of the second operating state of the injection-locked oscillators. Thus, the injection signal 120 is proportional to the signal at the input of the amplification circuit 108 and has a phase shift of approximately 180° relative to the input signal of the amplification circuit 108. In this example, the injection signal 120 is a spectrum comprising a line associated with each excitation signal 122. Each line in the spectrum of the injection signal 120 has an amplitude that is a function of the corresponding spin state. Therefore, using a spectrum provides a simple representation suitable for processing the injection signal by the injection-locked oscillators 106. In particular, this can limit errors related to false alarms and / or non-detection. The device 100 is thus more accurate.

[0042] The injection signal 120 at the output of the amplification circuit 108 travels through the feedback loop 114 in order to be injected into the various injection-locked oscillators 106 of the device 100. The signal injected into each injection-locked oscillator 106 is thus proportional to the injection signal 120.

[0043] There FIGURE 3 is a schematic representation of device 100 when one of the spin qubits of device 100 goes to the high state.

[0044] In the case of the FIGURE 3 The spin qubit numbered 1 is in a high state. For example, the output signal of the first electrometer 104 is on the order of nA, therefore greater than the output signals of the other electrometers 1042, 1043, and 1044, which are on the order of pA. Thus, in the signal at the input of the first amplification circuit 108, the first line at frequency f1 has an amplitude greater than the lines at frequencies f2, f3, and f4. The same is true of the injection signal 120 at the output of the amplification circuit 108.

[0045] In the example of the FIGURE 3 The signal reinjected into each injection-locked oscillator 106 contains all the components of the injection signal 120. Following this example, the amplitude of the injection signal 120 of the line positioned at frequency f1 is greater than or equal to a threshold. The first injection-locked oscillator 106 transitions to the second operating state. The excitation signal 1221 at the output of the first injection-locked oscillator 1061 operating in the second operating state is lower than the excitation signal 1221 of the first injection-locked oscillator 1061 operating in the first operating state. The threshold that causes the oscillator 1061 to switch from its first to its second operating state depends on the oscillator's topology, its bias point, and whether it operates with voltage or current injection.For example, in the case of current injection, the threshold can be between 0.1 times and 1 times the oscillator bias current.

[0046] Conversely, the amplitudes of the injection signal 120 positioned at the respective frequency lines f2, f3, and f4 are lower than the thresholds defined from the excitation signal 122 emitted by the second, third, and fourth injection-locked oscillators 1062, 1063, and 1064 when they are in their initial operating state. Consequently, the second, third, and fourth injection-locked oscillators 1062, 1063, and 1064 retain their initial operating states. Their associated excitation signals 122 are therefore preserved; they are not diminished. Although the injection signal 120 includes lines at the different frequencies f1, f2, f3 and f4, the injection signal 120 at the frequency f1 does not interfere in the operation of the second, third and fourth excitation means 1062, 1063, 1064.

[0047] These characteristics make it possible to promote the "filtering" behavior of the injection-locked oscillators of the device according to the invention, which allows either the preservation of the "initial" excitation signal, i.e. the excitation signal initially emitted by each injection-locked oscillator, or a reduction or even a cessation of the emission of the excitation signal.

[0048] There FIGURE 4 is a schematic representation of device 100 when the first injection-locked oscillator 106 is operating in its second operating state. The signal emitted by the oscillator is a voltage signal, the impedance of the electrometer grid being practically infinite.

[0049] There FIGURE 5 is a schematic representation of device 100 when three spin qubits of device 100 are in the high state.

[0050] As illustrated in the example FIGURE 5 The first, third, and fourth spin qubits are in the high state. For example, the conductance associated with the second electrometer 104 2 is on the order of tens of nS, while those of the first, third, and fourth electrometers 104 1, 104 3, 104 4 are on the order of tens of pS.

[0051] Following this example, the output signal of the second electrometer 104 2 can be neglected. The signal at the input of the amplification circuit 108 can thus be simplified and written according to the following formula: I e , 108 = ∑ i = 1 4 I 106 i ≈ A 1 sin 2 πf 1 t + A 3 sin 2 πf 3 t + A 4 sin 2 πf 4 t

[0052] The injection signal 120 at the output of the amplification circuit 108 can thus be written as follows: I 108 ≈ − AA 1 sin 2 πf 1 t − AA 3 sin 2 πf 3 t − AA 4 sin 2 πf 4 t With A corresponding to the amplification factor of the amplification circuit 108.

[0053] Following this example, the injection signal 120 contains the frequency components corresponding to the electrometers 104 for which the associated qubit is high. Following this example, the signal reinjected into the first, third, and fourth injection-locked oscillators 1061, 1063, 1064 is proportional to the injection signal 120 and thus comprises lines of amplitudes of the same order of magnitude. The first, third, and fourth injection-locked oscillators 1061, 1063, 1064 will therefore transition to their second operating state, which causes a significant decrease in the excitation signal 122 at the output of these injection-locked oscillators 1061, 1063, 1064. Conversely, the signal injected into the second injection-locked oscillator 106 2 does not contain, or contains only a very small component at the frequency f 2.Therefore, the second injection-locked oscillator 106 2 remains in its initial operating state. The excitation signal of the second injection-locked oscillator 106 2 is thus preserved, i.e., it is not diminished. Consequently, the excitation signal 122 2 of the second injection-locked oscillator 106 2 oscillates at the same amplitude.

[0054] There FIGURE 6 is a schematic representation of the behavior of the first, third and fourth injection-locked oscillators 106 1 , 106 3 , 106 4 device 100 after the transition to the high state of three spin qubits of device 100.

[0055] Following this example, the first, third and fourth excitation means 106 1 , 106 3 , 106 4 have switched to the second mode of operation.

[0056] There FIGURE 7 is a second example of device 700 according to the invention.

[0057] The 700 device illustrated in FIGURE 7 includes all elements of device 100. Thus, only the differences will be described.

[0058] The device 700 further comprises several measurement means 702, numbered 7021, 7022, 7023, and 7024 respectively, each coupled to an injection-locked oscillator 106. Each measurement means 702 is arranged to detect the operating state of the injection-locked oscillator 106 to which it is coupled and, depending on the detected state, emits a measurement signal related to a spin state. Thus, the analysis of the injection signal 122 emitted by each injection-locked oscillator 106 provides information on the state of the corresponding spin qubit. Consequently, in the device according to the invention, the spin qubits can be read directly by analyzing the excitation signals 122, which further improves the compactness of the device according to the invention as well as its low energy consumption. Furthermore, this promotes its ease of implementation because information processing is facilitated.

[0059] By way of non-limiting example, each measuring means 702 includes an analog comparator 704 connected at its input to the output of one of the injection-locked oscillators 106 and coupled at its output to a digital processing means 706. The analog comparator 704 is arranged to detect the operating mode of the injection-locked oscillator 106, that is, the first or second operating state of the injection-locked oscillator 106 to which it is connected. For example, each analog comparator 704 continuously records the excitation signal 122 of the corresponding injection-locked oscillator 106 and outputs a signal that varies according to the excitation signal 122. In the example illustrated in FIGURE 7 , the negative input of the analog comparator 704 is fixed at a potential and the positive input of the analog comparator 704 is fixed to the output of the corresponding injection-locked oscillator 106.

[0060] For a given measuring means 702, when the oscillator 106 is operating in its first state of operation, for example when no significant decrease in the excitation signal 122 is recorded by the analog comparator 704, then the output of the excitation signal 122 of the injection-locked oscillator 106 passes successively above and then below the potential of the negative input of the analog comparator 704. The output of the analog comparator 704 can thus be a square wave whose frequency is equal to that of the injection-locked oscillator 106.

[0061] When the injection-locked oscillator 106 operates in its second operating state, for example when a significant decrease in the excitation signal 122 is recorded by the comparator 704, then the excitation signal 122 never passes above or below the potential of the negative input of the analog comparator 704. The signal emitted at the output of the analog comparator 704 is thus a constant signal.

[0062] The signal emitted by the analog comparator 704 is transmitted to the digital processing unit 706, which outputs a digital signal that can have two states, 0 or 1, representing the spin state of the corresponding spin qubit. For example, state 0 represents a low spin state, while state 1 represents a high spin state.

[0063] Alternatively, the circuit illustrated in FIGURE 7 The circuit may include several biasing circuits 118 (schematic illustration), each coupled to an electrometer 104 and arranged to apply a DC bias voltage to said electrometer 104, adapted so that each electrometer 104 operates in Coulomb blockade. Following this example, the DC bias voltage may be applied to the input electrode of each electrometer 104, for example, to the drain and gate of each electrometer. In this example, all the electrometers 104 are biased with DC bias voltages of the same value. The biasing circuits 118 may also be implemented on the device 100.

[0064] Preferably, the 104 electrometers are biased to obtain a strong difference in conductance within them depending on the spin orientation of the charges in the spin qubits. This results in output signals of different amplitudes depending on the spin orientation. For example, the current through a 104 electrometer can be on the order of pA if an electron in the spin qubit's quantum dot has its spin oriented downwards, and on the order of nA if the electron in the spin qubit's quantum dot has its spin oriented upwards.

[0065] There FIGURE 8 illustrates a second example of a measuring means 702 that can be implemented in devices 100 or 700. This example focuses on the measuring means associated with the first injection-locked oscillator 106 1. Of course, the measuring means 702 illustrated in FIGURE 2 can be coupled to any injection-locked oscillator 106 of the device 100 or 700 according to the invention. The measuring means 702 associated with each injection-locked oscillator 106 may be similar or different.

[0066] In this example, the signal 122 1 is emitted by the first injection-locked oscillator 106 1. The measuring means 702 comprises a first comparator 802 and a second comparator 804, a gate 806, a current source system 808, and a capacitor 810. The measuring means illustrated in FIGURE 8 It also includes two locking devices, designated 812 and 814 respectively, and known by the English name "D latch" system. The measuring means illustrated in FIGURE 8 It also includes a delay line 816 and a CMOS switch 818. The second comparator 804 is arranged to output a signal that alternately comprises two states, a low state 0 and a high state 1. The current source 808 is arranged to continuously supply the capacitor 810.

[0067] When the first injection-locked oscillator 106 1 is in its first operating state, that is, when the injection signal 122 1 is maintained, then the first comparator 802 outputs an oscillating signal. At each rising or falling edge of this signal, flip-flops 812 (for rising edges) and 814 (for falling edges) close switch 818 for a time determined by the delay line 816 (the gate 806 allows the control signals from the locks to be combined). The voltage across the capacitor cannot therefore increase, and the output of comparator 804 remains low. If, on the other hand, the first injection-locked oscillator 106 1 is in its second operating state, the amplitude of the injection signal 122 1 has a lower value, which prevents the first comparator 802 from switching.The output of switch 810 therefore remains at a low level, and switch 818 remains in its open state. Under these conditions, the voltage across capacitor 810 increases linearly until it causes the output of comparator 804 to switch to its high level.

[0068] There FIGURE 9 illustrates an example of a 108 amplification circuit that can be implemented in 100 or 700 devices.

[0069] In the example illustrated in FIGURE 9 The amplification circuit 108 may include an amplifier 902 comprising a resistive feedback 904. The amplification circuit 108 is illustrated in FIGURE 9 is a transimpedance amplifier. The resistive feedback 904 is arranged to convert the signal at the input of the amplification circuit 108 into an injection signal 120 relative to a voltage. In the case illustrated in FIGURE 9 The gain of the amplification circuit 108 is proportional to the resistance present in the resistive feedback loop 904. As a non-limiting example, the gain of the amplification circuit 108 illustrated in FIGURE 9 is on the order of MΩ. The amplification circuit 108 can have a bandwidth between 10 and 30 MΩ, a gain of 10 MΩ, an input noise on the order of 10 fA / sqrt(Hz), and a power consumption on the order of a hundred microwatts. In the device 100 or 700, the bandwidth of the amplification circuit 108 is chosen so that all frequencies of all excitation signals 122 are within this bandwidth.

[0070] Of course, other arrangements can be implemented in the device according to the invention, such as those described in L. Le. Guevel 2020.

[0071] There FIGURE 10 illustrates another example of an amplification circuit 108 that can be implemented in devices 100 or 700.

[0072] The amplification circuit illustrated in FIGURE 100 is arranged to perform current amplification. Thus, in this example, the injection signal 122 is related to a current. In this case, the feedback loop 114 of device 100 or 700 is connected to a current input port of each injection-locked oscillator 106.

[0073] The 108 amplification circuit illustrated in FIGURE 10 is carried out according to the characteristics described in the Bonteanu 2017 document.

[0074] There FIGURE 11 illustrates an example of an injection-locked oscillator 106. The injection-locked oscillator 106 illustrated in FIGURE 6 is, for example, the first injection-locked oscillator 106 1. The injection-locked oscillator 106 1 illustrated on the FIGURE 11 includes an LC-type architecture, known in English as « cross-coupled differential topology with an NMOS pair and a tail-current at the source ». The injection-locked oscillator includes an 1100 resonance circuit known in English as the "LC tank". The resonance circuit comprises two inductors 1102 and 1104, a capacitor 1106, two CMOS transistors 1111 and 1112, and a current source 1114 to generate a bias current 1190. The gate of transistor 1111 is connected to the drain of transistor 1112 and vice versa, and the drains of both transistors are connected to the resonance circuit 1100. In this type of architecture, the excitation signal 122 emitted by the injection-locked oscillator 106 exhibits damping due to energy losses in the inductors 1102 and 110 and the capacitor 1106. To compensate for this damping, the NMOS transistors 1111 and 1112, as well as the current source 1114, act as a "negative resistance," injecting energy into the injection-locked oscillator. 106, and maintain it in an undamped oscillating state.The energy injected by transistors 1111 and 1112 and current source 1114 compensate for resistive losses in resonance circuit 1100.

[0075] The excitation signal 122 1 emitted by the injection-locked oscillator 106 1 illustrated in FIGURE 11 includes a frequency which is written according to the formula: f i = 1 2 π 1 L C with L corresponding to the total inductance of the resonance circuit 1110, and C to the total capacitance of the resonance circuit 1100. This arrangement allows for the optimization of the oscillation frequency specific to each injection-locked oscillator 106, as well as simplifying the adjustment of this frequency. Thus, following this arrangement, the excitation signal 122 illustrated in FIGURE 11 includes a natural oscillation frequency.

[0076] The oscillation frequency of the injection-locked oscillator 106 1 can be capacitively adjusted. This facilitates adaptability and / or modification of the frequency of each excitation signal 122, both in terms of its initial value and its potential modification. Furthermore, since the oscillation frequency of the injection signal 122 1 emitted by the injection-locked oscillator 106 1 depends on the total capacitance and inductance of the resonant circuit 1100, the oscillation frequency fi can be easily adjusted and / or modified by changing the total inductance and / or capacitance of the resonant circuit 1100. The oscillation frequency of each injection-locked oscillator 106 can be capacitively adjusted.For example, the first injection-locked oscillator 106 1 can have a total capacitance equal to C1 = Cref (typically between 10fF - femtofarads - and 1 pF - picofarad, depending on the desired oscillation frequency), the second injection-locked oscillator 106 2 can have a total capacitance equal to C2 = 22 < Cref = 4Cref, the third injection-locked oscillator 106 3 can have a total capacitance equal to C3 = 23 < Cref = 8Cref, and the fourth injection-locked oscillator 106 4 can have a total capacitance equal to C4 = 24 < Cref = 16Cref. The total capacitance value of each injection-locked oscillator 106 can be programmable. For example, device 100 or 700 may include a plurality of switches coupled to a memory arranged to adjust the total capacity of each injection-locked oscillator 106.Thus, the capacity of each injection-locked oscillator 106 can be adjusted more precisely.

[0077] The injection-locked oscillator 106 1 illustrated in FIGURE 11 includes an input port 1108 which can be a current input port or a voltage input port. If port 1108 is a voltage input port, an output voltage from amplifier 110 drives the current source I108 with a certain transconductance gain. If, on the other hand, port 1108 is a current input port, an output current from amplifier 110 is copied (with, where applicable, a gain) by the current source I108. Thus, the injection signal can be a voltage or a current, which makes it possible to propose an injection-locked oscillator that is easy to implement in the device according to the invention. In the case of using the current input port, the injection-locked oscillator 106 1 of this example can be coupled to the amplification circuit 108 illustrated in FIGURE 10 In the case where the injection signal 120 is relative to a voltage, for example when the amplification circuit 108 contains a resistive feedback loop as illustrated in FIGURE 9 The amplification circuit 108 can be coupled with a transconductance amplification stage, for example, a MOS transistor arranged to convert an input voltage on the gate of the MOS transistor into a drain-source current.

[0078] In the illustrated example, when the injection signal 120 (here related to a current) does not contain a line at the frequency of the injection-locked oscillator 106 1, the injection signal 120 has no impact on the dynamics of the injection-locked oscillator 106 1. Consequently, the excitation signal 122 1 emitted by the injection-locked oscillator 106 1 remains unchanged. This is because the injection signal 120 is filtered by the LC resonant circuit.

[0079] The simplified transfer function relating the output voltage of the injection-locked oscillator 106 1 to the injection signal 120 can be expressed according to the following formula: H = V 106 I 108 = j L 2 ω 1 − w 0 w 2 = L 2 ω w 2 w 0 1 − w w 0 2 With I108 corresponding to the injection signal 120 related to a current and V106 corresponding to the output voltage of the injection-locked oscillator 106 1. Thus, in the illustrated example, the transfer function is minimal for w = w0. As explained above with reference to the figure 9 When the amplitude of the injection signal 120, at the corresponding spectral line, is below a threshold, the injection-locked oscillator 106 1 operates in its first operating state. The excitation signal 122 1 of the injection-locked oscillator 106 1 remains unchanged.

[0080] When the amplitude of the injection signal (120), at the corresponding line, is greater than or equal to the threshold, the injection-locked oscillator 106 switches to its second operating mode. The excitation signal 122 decreases. Indeed, in the example illustrated in FIGURE 11 The transfer function increases, and therefore the impact of the injection signal 120 on the dynamics of the injection-locked oscillator 1061, illustrated by the previous equation, is no longer negligible. The injection signal 122 opposes the operation of the injection-locked oscillator 1061. The excitation signal 1221 emitted by the injection-locked oscillator 1061 operating in its first state typically has an amplitude at least 10 times greater than that of the excitation signal 122 emitted by the injection-locked oscillator 1061 operating in its second state.For example, the amplitude of the excitation signal 122 1 emitted by the injection-locked oscillator 106 1 when operating in its first state can be on the order of a few hundred mV, while when it is in its second state of operation, the signal emitted by the injection-locked oscillator 106 1 can be on the order of a few tens of mV. The amplitude of the excitation signal 122 1 emitted by the injection-locked oscillator 106 1 operating in its second state of operation depends on the injection signal 120 and the bias current of the injection-locked oscillator 106 1 when it is in its first state of operation. This allows the attenuation value of injection-locked oscillators operating in their second state of operation to be adjusted.Therefore, the decrease in the injection signal can be small, allowing the excitation signal to continue driving the corresponding electrometer. Conversely, the decrease can be significant, which can lead to the emission of an excitation signal that prevents the corresponding electrometer from being driven, or it can even cause the injection-locked oscillator to shut down.

[0081] Of course, the arrangement of the injection-locked oscillator 106 1 is not limited to the example below. Other arrangements of injection-locked oscillators 106 are applicable to the operation of the injection-locked oscillators 106 used in the device according to the invention. For example, the injection-locked oscillator 106 1 may include an LC structure known by the English name " NMOS pair and tail current at the drain ", Or " PMOS pair and tail current at the source », « PMOS pair and tail current at the drain or more complex LC architectures, such as a topology « CMOS Core Cross-coupled differential topologies ».

[0082] In devices 100 or 700, the injection-locked oscillators 106 can all be identical; for example, they can all have the arrangement described in FIGURE 11 , or they may include a different arrangement from one sociator to another.

[0083] There FIGURE 12 is another example of a quantum device 1200 according to the invention.

[0084] In the device illustrated in FIGURE 12 , the spin qubits are arranged in a spin qubit matrix 1202 comprising n rows along a first direction 1204 and m columns along a second direction 1206.

[0085] In the 1200 device, the 104 electrometers are arranged in the form of a matrix (not shown) positioned with respect to the 1202 spin qubit matrix so that at least one quantum dot of each spin qubit is capacitively coupled to a quantum dot of one of the 104 electrometers.

[0086] In the example illustrated in FIGURE 12 The spin qubit matrix comprises n rows and m columns, where n and m are integers greater than or equal to 1, which may be equal or different. The 10⁴ electron matrix is ​​arranged above or below the 12⁰² spin qubit matrix such that the quantum dot of each spin qubit is capacitively coupled to a quantum dot of one of the 10⁴ electrons located near, above, or below the quantum dot of each spin qubit. In this example, the electron matrix comprises n rows and m columns.

[0087] The parameters n and m can typically take values ​​between 10 and 1000. As an example, n and m can be 100.

[0088] The spin 1202 qubit matrix and the electron matrix can be realized in a superimposed manner via the implementation of a 3D integration process.

[0089] In the example illustrated in FIGURE 12 In this embodiment, the device 1200 comprises n excitation means 106 arranged along the first direction. Each injection-locked oscillator 106 is coupled to all the electrometers 104 coupled to spin qubits positioned on the same row of the spin qubit matrix 1202. All the electrometers 104 arranged on the same row of the spin qubit matrix 1202 are coupled to the same injection-locked oscillator 106 such that the same excitation signal 122 is applied to at least one input electrode of the electrometers 104 present on the same row of the electrometer matrix.

[0090] In device 1200, the amplification circuit 108 also includes m amplifiers 110 arranged in the second direction. Each amplifier 110 is coupled to all the electrometers 104 coupled to spin qubits positioned in the same column of the spin qubit matrix 1202, the output of each amplifier 110 being coupled to the input of an injection-locked oscillator 106. In this way, all the output signals delivered by the electrometers present in the same column of the electrometer matrix are summed before being sent to the corresponding amplifier 110.

[0091] Thus, each column of the spin qubit matrix 1202 (coupled to the electrometers) associated with an injection-locked oscillator 106 and an amplifier 110 of the amplification circuit corresponds to device 100. The operation of device 1200 is therefore similar to that of device 100.

[0092] The device 1200 also includes m switches arranged in the second direction and positioned upstream or, preferably, downstream of the amplification circuit 108. Each switch is arranged to alternately connect all the electrometers 104 coupled to spin qubits positioned on the same column of the spin qubit matrix 1202 to the corresponding amplifier 110 or to the corresponding injection-locked oscillator 106.

[0093] The 1200 device may also include biasing circuits coupled to each electrometer 104.

[0094] In addition, the device 1200 also includes a measuring means 1208 coupled to the output of each injection-locked oscillator 106.

[0095] There FIGURE 13 is another example of a quantum device 1300 according to the invention. The device 1300 comprises all the elements of the device 1200. Only the differences with the FIGURE 12 will be described.

[0096] The amplification circuit 108 comprises a single amplifier 110. The device 1300 further comprises m switches (not shown) arranged in the second direction, each switch being arranged to alternately connect all the electrometers 104 coupled to spin qubits positioned on the same column of the spin qubit matrix 1202 to the amplifier 110.

[0097] Depending on the variant of the 1200 and 1300 devices, the device can read a spin qubit matrix containing several thousand spin qubits. Energy consumption and device compactness are improved compared to a device that does not perform spin qubit matrix reading. The switches in these devices are arranged to perform a sequential read of the 1202 spin qubit matrix. Specifically, the read is performed column by column of the 1202 spin qubit matrix.

[0098] The variant described following the 1300 device can be preferred because it only requires the use of one amplifier in the amplification circuit for the entire spin qubit matrix. Consequently, this version requires fewer electronic components (in this case, fewer amplifiers), which improves compactness and reduces power consumption.

[0099] In variants of devices 1200 and 1300, the 104 electrometer matrix comprises fewer electrometers than spin qubits present in the 1202 spin qubit matrix. Devices 1200 and 1300 may in this case include a processing unit arranged to recover, by triangulation, the state of each spin qubit from a signal emitted by each 104 electrometer. The processing unit may include a computer and / or a processor and / or a computing module.

[0100] There FIGURE 14 is a schematic representation of a first example of method 1400 according to the invention. Method 1400 is a method for reading several spin 102 qubits, each comprising a quantum dot. Method 1400 is arranged to be implemented by any one of the devices 100, 700, 1200, and 1300.

[0101] The 1400 process illustrated in FIGURE 14uses the electrometers 104, each being capacitively coupled to a potential well of at least one quantum dot of at least one of the spin qubits 102, the injection-locked oscillators 106 each being coupled to at least one electrode of one of the electrometers 104, the amplification circuit 108, said amplification circuit 108 being coupled to the output of each electrometer 104 and comprising at least one amplifier 110 and an output 112, said method comprising: an emission 1402 by each injection-locked oscillator 106 of the excitation signal 122 on at least one input electrode of the electrometer 104 to which it is coupled, each excitation signal 122 having a different frequency, characterized in that said method 1400 further comprises: an injection 1406 of the injection signal 120, into each injection-locked oscillator 106 by the feedback loop 114 coupling the output 112 of said amplification circuit 108 to the input of each injection-locked oscillator 106, the injection signal 120 comprising components at the frequencies of said excitation signals 122, and for each injection-locked oscillator 106, a decrease 1408 or a preservation 1410 of the excitation signal 122 as a function of said injection signal.

[0102] The method according to the invention offers a solution for reading multiple spin qubits that is simple to implement and designed to use as few electronic components as possible. Consequently, the method provides advantages similar to those of the device according to the invention, particularly in limiting the energy consumption of the components implementing the method. List of documents cited

[0103] Vandersypen 2016 : « Interfacting spin qubits in quantum dots and donors - hot, dense and coherent", ARXIV.ORG, 18 décembre 2016, DOI: 10.1038 / S41534-0038-Y Bonteanu 2017 : A current controlled CMOS current amplifier», G. Bonteanu, DOI : 10.1109 / ISEEE.2017.8170668 L. Le. Guevel 2020 : L. Le. Guevel et al., "19.2 A 110mK 295µ W 28nm FDSOI CMOS Quantum Integrated Circuit with a 2.8GHz Excitation and nA Current Sensing of an On-Chip Double Quantum Dot," 2020 IEEE International Solid- State Circuits Conference - (ISSCC), San Francisco, CA, USA, 2020, pp. 306-308, doi: 10.1109 / ISSCC19947.2020.9063090. Yoon 2004: Sangwoong Yoon, « LC-tank CMOS Voltage-Controlled Oscillators using High Quality Inductors Embedded in Advanced Packaging Technologies », Geogia Institute of technology 2004 Reilley 2007 : « Fast single-charge sensing a RF quantum point contact » D. J Reilley et al., APPLIED PHYSICS LETTERS 91, 162101, 2007

Claims

1. Quantum device (100, 700, 1200, 1300) comprising: - multiple spin qubits (102), each comprising at least one quantum dot, - multiple electrometers (104), each being capacitively coupled to a potential well of the at least one quantum dot (102) of at least one of the spin qubits, and - multiple injection-locked oscillators (106), each being coupled to at least one electrode of one of the electrometers (104) and designed to transmit an oscillating signal (122), called an excitation signal (122), to at least one input electrode of the electrometer (104) to which it is coupled, each excitation signal (122) having a different frequency, characterized in that it also comprises - an amplification circuit (108) comprising at least one amplifier (110), said amplification circuit (108) being coupled to the output of each electrometer (104) and comprising an output (112), and in that said device (100, 700, 1200, 1300) comprises a feedback loop (114) coupling the output (112) of said amplification circuit (108) to an input of each injection-locked oscillator (106) and through which an electrical signal (120), called an injection signal (120), flows, comprising components at the frequencies of said excitation signals (122), each injection-locked oscillator (106) being designed to receive the injection signal (120) and, as a function of said injection signal (120), keep its excitation signal (122) in a first operating state or decrease its excitation signal (122) in a second operating state.

2. Device (100, 700, 1200, 1300) according to the preceding claim, wherein the injection signal (120) has a spectrum comprising a line associated with each excitation signal (122), each line of said spectrum having an amplitude that is dependent on a state of the spin qubit.

3. Device (100, 700, 1200, 1300) according to the preceding claim, wherein each injection-locked oscillator (106) is designed to: - operate in its first operating state when the amplitude of the injection signal (120), at the corresponding spectral line, is below a threshold, and - operate in its second operating state when the amplitude of the injection signal (120), at the corresponding spectral line, is greater than or equal to said threshold.

4. Device (100, 700, 1200, 1300) according to any one of the preceding claims, wherein, for each injection-locked oscillator (106), the excitation signal (122) transmitted in the first operating state is at least ten times greater than the excitation signal (122) transmitted in the second operating state.

5. Device (700, 1200, 1300) according to any one of the preceding claims, comprising multiple measurement means (702, 1208), each being coupled to an injection-locked oscillator (106), each measurement means (702, 1208) being designed to detect the operating state of said injection-locked oscillator (106) and, depending on the detected state, to transmit a signal, called a measurement signal, relating to a spin state.

6. Device (100, 700, 1200, 1300) according to any one of the preceding claims, wherein the amplification circuit (108) is designed to negatively amplify a signal output by the electrometers.

7. Device (100, 700, 1200, 1300) according to any one of the preceding claims, wherein the amplification circuit (108) is designed to perform current amplification or, when the at least one amplifier (110) of the amplification circuit (108) comprises at least one transimpedance amplifier, designed to convert an input signal into a voltage at the output (112) of said amplification circuit (108).

8. Device (100, 700, 1200, 1300) according to any one of the preceding claims, wherein each electrometer (104) comprises a drain, and a gate, the injection-locked oscillators (106) being coupled to the drain or to the gate.

9. Device (100, 700, 1200, 1300) according to any one of the preceding claims, wherein each electrometer (104) comprises a quantum point contact or a single-electron transistor.

10. Device (100, 700, 1200, 1300) according to any one of the preceding claims, comprising multiple bias circuits, each being coupled to an electrometer (104) and arranged to apply a DC bias voltage to said electrometer (104) which is designed so that each electrometer produces a Coulomb blockade.

11. Device (1200, 1300) according to any one of the preceding claims, wherein: - the spin qubits are arranged in a spin qubit array (1202) comprising n rows in a first direction and m columns in a second direction, and - the electrometers (104) are arranged in the form of an array positioned facing the spin qubit array (1202) so that the at least one quantum dot of one of the electrometers is capacitively coupled to at least one quantum dot of at least one spin qubit.

12. Device (1200) according to Claim 11, wherein the amplification circuit (108) comprises: - m amplifiers (110) arranged in the second direction, each amplifier (110) being coupled to all of the electrometers (104) coupled to spin qubits positioned on one and the same column of the spin qubit array (1202), the output of each amplifier (110) being coupled to the input of the injection-locked oscillator (106), said device (1200) further comprising: - n excitation means (106) arranged in the first direction, each injection-locked oscillator (106) being coupled to all of the electrometers (104) coupled to spin qubits positioned on one and the same row of the spin qubit array (1202), - m switches arranged in the second direction and positioned upstream or downstream of the amplification circuit (108), each switch being arranged so as to alternately connect all of the electrometers (104) coupled to spin qubits positioned on one and the same column of the spin qubit array (1202) to the corresponding amplifier (110) or to the corresponding injection-locked oscillator (106):

13. Device (1300) according to Claim 11, comprising: - n excitation means (106) arranged in the first direction, each injection-locked oscillator (106) being coupled to all of the electrometers (104) coupled to spin qubits positioned on one and the same row of the spin qubit array (1202), the amplification circuit (108) comprising a single amplifier (110), said device (1300) further comprising: - m switches arranged in the second direction, each switch being arranged so as to alternately connect all of the electrometers (104) coupled to spin qubits positioned on one and the same column of the spin qubit array (1202) to the amplifier (110), the output of the amplifier (110) being coupled to each injection-locked oscillator (106).

14. Device (1200, 1300) according to either one of Claims 12 and 13, wherein each spin qubit alternately comprises two states, a high state and a low state, when a quantum dot of one of the electrometers is coupled to at least one quantum dot of at least two spin qubits, said device further comprising a processing unit configured to retrieve, by triangulation, the state of each spin qubit from a signal transmitted by each electrometer, said signal being dependent on the state of the spin qubit15. Method (1400) for reading multiple spin qubits (102), each comprising a quantum dot, said method (1400) using multiple electrometers (104), each being capacitively coupled to a potential well of the at least one quantum dot of at least one of the spin qubits (102), multiple injection-locked oscillators (106), each being coupled to at least one electrode of one of the electrometers (104), an amplification circuit (108), said amplification circuit (108) being coupled to the output of each electrometer (104) and comprising at least one amplifier (110) and an output (112), said method comprising: - each of the injection-locked oscillators (106) transmitting (1402) an oscillating signal, called an excitation signal (122), to at least one input electrode of the electrometer (104) to which it is coupled, each excitation signal (122) having a different frequency, characterized in that said method (1400) further comprises: - injecting (1406) a signal (120), called an injection signal (120), into each injection-locked oscillator (106) via a feedback loop (114) coupling the output (112) of said amplification circuit (108) to the input of each injection-locked oscillator (106), the injection signal (120) comprising components at the frequencies of said excitation signals (122) and, for each injection-locked oscillator (106), decreasing (1408) or maintaining (1410) the excitation signal (122) resulting from said injection signal.