Method for reading out the states of several, in particular superconducting, qubits, readout device and quantum computer

Abstract

The invention relates to a method for reading out the states of several, in particular superconducting, qubits (Q1-Qn), preferably flux qubits, wherein the same probe signal (7) is supplied to the qubits (Q1-Qn) for reading out the states via a common probe line (8), and wherein each qubit (Q1-Qn) is assigned its own response circuit (5), preferably having a response resonator (4), and wherein, in response to the supplied probe signal (7), a response signal (20) with information about the state of the respective qubit (Q1-Qn) is output via the respective response circuit (5), wherein the response signal (20) of at least one qubit (Q1-Qn) is delayed relative to the response signal (20) of at least one further qubit (Q1-Qn).

Claims

[1] Method for reading out the states of several, in particular superconducting, qubits (Q1-Qn), preferably flux qubits, wherein the same sample signal (7) is supplied to the qubits (Q1-Qn) for reading out the states via a common sample line (8), and wherein each qubit (Q1-Qn) is assigned its own response circuit (5), preferably having a response resonator (4), and wherein in response to the supplied sample signal (7) via the respective response circuit (5) a response signal (20) with information about the state of the respective qubit (Q1-Qn) is output, characterized by that the response signal (20) of at least one qubit (Q1-Qn) is delayed relative to the response signal (20) of at least one further qubit (Q1-Qn). [2] Method according to claim 1, characterized bythat the response signals (20) of the qubits (Q1-Qn) are time-variable and the delay of the response signal of at least one qubit (Q1-Qn) is carried out while maintaining the time-variable character. [3] Method according to claim 1 or 2, characterized by that the delay of the response signal (20) of the at least one qubit (Q1-Qn) is achieved with at least one delay device (19) associated with and / or in particular directly connected downstream of the response circuit (5) of the at least one qubit (Q1-Qn). [4] Method according to one of claims 1 to 3, characterized by that all response signals (20) are delayed to different degrees. [5] Method according to one of claims 1 to 3, characterized by that exactly one response signal (20) is not delayed and the remaining response signals (20) are delayed to different degrees. [6] Method according to one of the preceding claims, characterized bythat response signals (20) originating from different qubits (Q1-Qn) pass through different numbers of delay devices (19). [7] Method according to one of the preceding claims, characterized by that the response signals (20) of the plurality of qubits (Q1-Qn) are combined, in particular summed, to obtain a common response signal (21), preferably within a qubit chip (2) also comprising the qubits (Q1-Qn) and / or using a passive or active circuit. [8] Method according to claim 7, characterized by that the common response signal (21) is fed to a common readout device for further processing, preferably via a common transmission line. [9] Method according to claim 7 or 8, characterized by that the common response signal (21) is analyzed to obtain information about the states of the plurality of qubits (Q1-Qn). [10] Method according to claim 9, characterized bythat a particularly digitized front (23) of the common response signal (21) is analyzed in order to obtain the information about the states of the plurality of qubits (Q1-Qn). [11] Method according to claim 9, characterized by that at least one amplitude and / or at least one zero crossing of the common response signal (21), in particular the time position of at least one zero crossing of the common response signal, and / or the time position of at least one peak contained in the common response signal (21) is determined in order to obtain the information about the states of the plurality of qubits (Q1-Qn). [12] Method according to claim 8 or any one of claims 9 to 11, as far as dependent on claim 8, characterized by that the sample signal (7) is used to trigger the common readout device. [13] Method according to one of the preceding claims, characterized bythat the response signals (20) belonging to different qubits (Q1-Qn) have the same frequency components for the same qubit states. [14] Method according to one of the preceding claims, characterized by that the response circuits (5) of the qubits (Q1-Qn) each comprise a response resonator (4), in particular, wherein the response resonators (4) of the different qubits (Q1-Qn) coincide with regard to their resonance frequency, preferably, wherein the response resonators (4) of different qubits (Q1-Qn) are of identical construction. [15] Method according to one of the preceding claims, characterized by that the response signal (20) of at least one qubit (Q1-Qn) is delayed by 0.5 ns to 10 ns compared to the response signal (20) of at least one further qubit (Q1-Qn). [16] Readout device for carrying out the method according to one of claims 1 to 15, comprising a plurality of response circuits (5), preferably having a response resonator (4), which are each connected or connectable to a qubit (Q1-Qn), and at least one delay device (19) which is assigned to at least one response circuit (5) and / or in particular is connected directly downstream and can delay a response signal (20) output by the at least one response circuit (5), which contains information about the state of a qubit (Q1-Qn). [17] Reading device according to claim 16, characterized bythat the at least one delay device (19) is designed and / or arranged such that it can delay a time-variable response signal (20) while maintaining its time-variable character, and / or that the at least one delay device (19) is designed and / or arranged to effect a fixed delay. [18] Reading device according to claim 16 or 17, characterized by that a plurality of delay devices (19) are provided, wherein different delay devices (19) can cause delays of qubit response signals (20) of different lengths, and / or wherein the readout device is designed such that response signals (20) originating from different qubits (Q1-Qn) pass through a different number of delay devices (19). [19] Reading device according to one of claims 16 to 18, characterized bythat the response circuits (5) each have a response resonator (4), in particular, wherein the response resonators (4) of different, preferably all, response circuits (5) are identical in terms of their resonance frequency, preferably, wherein the response resonators (4) of different, preferably all, response circuits (5) are of identical construction. [20] Quantum computer (1) comprising at least one readout device according to one of claims 16 to 19 and several qubits (Q1-Qn).

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